Trial Outcomes & Findings for Patient Experiences With the COVID-19 Vaccination After Breast Cancer Treatment (NCT NCT04872738)

Last Updated: 2026-01-06

Results Overview

The investigators expect 90% of participants to receive the COVID-19 vaccine on their contralateral (unaffected) arm. This outcome measure is looking at the number of participants who received the COVID-19 vaccine on the side of breast cancer treatment vs those who received the vaccine on the opposite side of breast cancer treatment. Patients with bilateral cancer were excluded from this analysis due to the nature of breast cancer laterality categorization.

Recruitment status

COMPLETED

Target enrollment

714 participants

Primary outcome timeframe

This was a survey study of patients with breast surgery for breast cancer. Participants replied to the online survey up to 361.5 months post their breast surgery (median 69.0 months). This was the study's reported timeframe in the published manuscript.

Results posted on

2026-01-06

Participant Flow

We excluded 44 incomplete surveys or surveys from patients who received the first vaccine prior to breast cancer treatment, resulting in data from 670 patients for analysis.

Participant milestones

Participant milestones
Measure	Vaccinated Breast Cancer Patients [mRNA Vaccine - Moderna, Pfizer] Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients [Non-mRNA Vaccine - Johnson & Johnson] Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).
Dose 1/Primary Series Survey STARTED	621	49
Dose 1/Primary Series Survey COMPLETED	621	49
Dose 1/Primary Series Survey NOT COMPLETED	0	0
Booster Survey STARTED	621	49
Booster Survey COMPLETED	469	34
Booster Survey NOT COMPLETED	152	15

Reasons for withdrawal

Reasons for withdrawal
Measure	Vaccinated Breast Cancer Patients [mRNA Vaccine - Moderna, Pfizer] Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients [Non-mRNA Vaccine - Johnson & Johnson] Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).
Booster Survey Did not respond or did not receive booster dose at the time of survey distribution	152	15

Baseline Characteristics

Race and Ethnicity were not collected from any participant.

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Vaccinated Breast Cancer Patients [mRNA Vaccine - Moderna, Pfizer] n=621 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine (Moderna, Pfizer) and Cohort 2 being those who received a non-mRNA vaccination (Johnson \& Johnson). Demographic data for Cohort 2 is not included, as this cohort was not included in the primary analysis and therefore its data was not pulled.	Vaccinated Breast Cancer Patients [Non-mRNA Vaccine - Johnson & Johnson] n=49 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Total n=670 Participants Total of all reporting groups
Age, Continuous	53 years n=621 Participants	53.8 years n=49 Participants	53.1 years n=670 Participants
Sex: Female, Male Female	621 Participants n=621 Participants	49 Participants n=49 Participants	670 Participants n=670 Participants
Sex: Female, Male Male	0 Participants n=621 Participants	0 Participants n=49 Participants	0 Participants n=670 Participants
Race and Ethnicity Not Collected	—	—	0 Participants Race and Ethnicity were not collected from any participant.
BMI, Continuous	26.0 kg/m² n=619 Participants • There was missing data for 2 participants in regards to BMI for the mRNA vaccine cohort and missing data for 3 participants in regards to BMI for the non-mRNA vaccine cohort.	27.2 kg/m² n=46 Participants • There was missing data for 2 participants in regards to BMI for the mRNA vaccine cohort and missing data for 3 participants in regards to BMI for the non-mRNA vaccine cohort.	26.0 kg/m² n=665 Participants • There was missing data for 2 participants in regards to BMI for the mRNA vaccine cohort and missing data for 3 participants in regards to BMI for the non-mRNA vaccine cohort.
BMI > 25	356 Participants n=619 Participants • There was missing data for 2 participants in regards to BMI for the mRNA vaccine cohort and missing data for 3 participants in regards to BMI for the non-mRNA vaccine cohort.	27 Participants n=46 Participants • There was missing data for 2 participants in regards to BMI for the mRNA vaccine cohort and missing data for 3 participants in regards to BMI for the non-mRNA vaccine cohort.	383 Participants n=665 Participants • There was missing data for 2 participants in regards to BMI for the mRNA vaccine cohort and missing data for 3 participants in regards to BMI for the non-mRNA vaccine cohort.
Mastectomy with Reconstruction	222 Participants n=621 Participants	11 Participants n=49 Participants	233 Participants n=670 Participants
Mastectomy without Reconstruction	51 Participants n=621 Participants	6 Participants n=49 Participants	57 Participants n=670 Participants
Lumpectomy	348 Participants n=621 Participants	31 Participants n=49 Participants	379 Participants n=670 Participants
Axillary Lymph Node Dissection	176 Participants n=621 Participants	18 Participants n=49 Participants	194 Participants n=670 Participants
Sentinel Lymph Node Biopsy	393 Participants n=621 Participants	24 Participants n=49 Participants	417 Participants n=670 Participants
No Nodal Surgery	52 Participants n=621 Participants	7 Participants n=49 Participants	59 Participants n=670 Participants
Regional Lymph Node Radiation	188 Participants n=621 Participants	20 Participants n=49 Participants	208 Participants n=670 Participants
Neoadjuvant +/- adjuvant chemotherapy	109 Participants n=621 Participants	11 Participants n=49 Participants	120 Participants n=670 Participants
Adjuvant chemotherapy, only	196 Participants n=621 Participants	14 Participants n=49 Participants	210 Participants n=670 Participants
Time between breast surgery and first dose	69.0 months n=621 Participants • There was missing data for 3 participants in regards to date of surgery for the non-mRNA vaccine cohort.	85.4 months n=46 Participants • There was missing data for 3 participants in regards to date of surgery for the non-mRNA vaccine cohort.	70.1 months n=667 Participants • There was missing data for 3 participants in regards to date of surgery for the non-mRNA vaccine cohort.

PRIMARY outcome

Timeframe: This was a survey study of patients with breast surgery for breast cancer. Participants replied to the online survey up to 361.5 months post their breast surgery (median 69.0 months). This was the study's reported timeframe in the published manuscript.

Population: The cohort of patients who received a non-mRNA vaccine was not included in the analysis, as only a small proportion of the population received this vaccine type. Consequently, data on this group were not collected.

Outcome measures

Outcome measures
Measure	Vaccinated Breast Cancer Patients Dose 1 [mRNA vaccine - Moderna, Pfizer] n=554 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Dose 2 [mRNA vaccine - Moderna, Pfizer] n=554 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [mRNA vaccine - Moderna, Pfizer] n=405 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients [non-mRNA vaccine - Johnson & Johnson] Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [non-mRNA vaccine - Johnson & Johnson] Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).
COVID-19 Vaccination on Contralateral vs Ipsilateral Arm Patients who received the vaccine contralateral to breast cancer treatment	432 Participants	435 Participants	331 Participants	—	—
COVID-19 Vaccination on Contralateral vs Ipsilateral Arm Patients who received the vaccine ipsilateral to breast cancer treatment	122 Participants	119 Participants	74 Participants	—	—

PRIMARY outcome

Population: The first row, 'Lymph node (LN) swelling, general', reports the number of subjects who reported LN swelling. We then analyzed, of the subjects who indicated that they experienced LN swelling, the laterality in which this swelling occurred. These data are represented in rows 2 through 5. In the analysis of LN swelling laterality related to both vaccine and BC laterality, the population size was the number of participants vaccinated on the specified side (only conducted for mRNA vaccines).

The investigators expect 10-15% of participants to experience lymph node swelling after receiving the Pfizer or Moderna vaccines. The outcome measure analyzes the number of participants who experienced LN swelling after receiving each dose of their COVID-19 vaccines. The analysis looked at what location on the body lymph node swelling occurred (axilla vs supraclavicular region), which side of the body this swelling occurred in relation to the side of the body that received the vaccine (ipsilateral vs contralateral), and which side of the body this swelling occurred in relation to the side of the body the patient has/had breast cancer (ipsilateral vs contralateral). Patients with bilateral cancer were excluded from the analysis of LN swelling in relation to both the vaccine and breast cancer laterality due to the nature of BC laterality categorization. Analysis on breast cancer laterality and LN swelling was not conducted for the non-mRNA vaccine (Johnson \& Johnson) group.

Outcome measures

Outcome measures
Measure	Vaccinated Breast Cancer Patients Dose 1 [mRNA vaccine - Moderna, Pfizer] n=621 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Dose 2 [mRNA vaccine - Moderna, Pfizer] n=621 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [mRNA vaccine - Moderna, Pfizer] n=469 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients [non-mRNA vaccine - Johnson & Johnson] n=49 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [non-mRNA vaccine - Johnson & Johnson] n=34 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).
Lymph Node (LN) Swelling After COVID-19 Vaccine Contralateral to vaccine and to BC (among pts who received dose ipsilateral to BC)	6 Participants	7 Participants	5 Participants	—	—
Lymph Node (LN) Swelling After COVID-19 Vaccine Lymph node (LN) swelling, general	61 Participants	80 Participants	53 Participants	4 Participants	1 Participants
Lymph Node (LN) Swelling After COVID-19 Vaccine LN swelling: Supraclavicular, Contralateral to Vaccine	11 Participants	16 Participants	5 Participants	0 Participants	0 Participants
Lymph Node (LN) Swelling After COVID-19 Vaccine LN swelling: Supraclavicular, Ipsilateral to Vaccine	18 Participants	21 Participants	17 Participants	1 Participants	0 Participants
Lymph Node (LN) Swelling After COVID-19 Vaccine LN swelling: Axillary, Contralateral to Vaccine	28 Participants	36 Participants	13 Participants	0 Participants	1 Participants
Lymph Node (LN) Swelling After COVID-19 Vaccine LN swelling: Axillary, Ipsilateral to Vaccine	33 Participants	50 Participants	38 Participants	3 Participants	0 Participants
Lymph Node (LN) Swelling After COVID-19 Vaccine LN swelling ipsilateral to vaccine, contralat. to BC (among pts who received dose contralat. to BC)	33 Participants	48 Participants	40 Participants	—	—
Lymph Node (LN) Swelling After COVID-19 Vaccine LN swelling contralat. to vaccine, ipsilateral to BC (among pts who received dose contralat. to BC)	30 Participants	42 Participants	12 Participants	—	—
Lymph Node (LN) Swelling After COVID-19 Vaccine Ipsilateral to vaccine and to BC (among pts who received dose ipsilateral to BC)	14 Participants	17 Participants	10 Participants	—	—

PRIMARY outcome

Population: The number analyzed reflects participants who experienced swelling at the specified location (axilla or supraclavicular) and the side relative to vaccine administration. For example, "Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: 24 hours or less" for Dose 1 included 11 patients, as 11 of 61 reported swelling in the supraclavicular region contralateral to the side they received the vaccine.

The outcome measure will be analyzing the reported duration of lymph node swelling, categorized by the location at which lymph node swelling occurred (the axilla vs supraclavicular region) and which side of the body this swelling occurred in relation to the side of the body that received the vaccine injection (ipsilateral vs contralateral). The main aim of this paper was to report the side effects of the mRNA COVID-19 vaccines in patients treated for breast cancer.

Outcome measures

Outcome measures
Measure	Vaccinated Breast Cancer Patients Dose 1 [mRNA vaccine - Moderna, Pfizer] n=61 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Dose 2 [mRNA vaccine - Moderna, Pfizer] n=80 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [mRNA vaccine - Moderna, Pfizer] n=53 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients [non-mRNA vaccine - Johnson & Johnson] n=4 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [non-mRNA vaccine - Johnson & Johnson] n=1 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: 24 hours or less	2 Participants	2 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: 48 hours or less	3 Participants	0 Participants	1 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: 4 weeks or less	0 Participants	2 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: 24 hours or less	6 Participants	8 Participants	3 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: 2 weeks or less	0 Participants	0 Participants	1 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: > than 4 weeks/still experiencing	3 Participants	4 Participants	4 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: I don't know	1 Participants	2 Participants	1 Participants	1 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: 24 hours or less	2 Participants	6 Participants	2 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: 48 hours or less	9 Participants	7 Participants	4 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: 2 weeks or less	3 Participants	0 Participants	1 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: 3 weeks or less	1 Participants	2 Participants	3 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: 24 hours or less	2 Participants	2 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: 48 hours or less	2 Participants	2 Participants	2 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: 1 week or less	6 Participants	9 Participants	5 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: More than 4 weeks/still experiencing	8 Participants	13 Participants	3 Participants	0 Participants	1 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: I don't know	3 Participants	1 Participants	2 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: 1 week or less	2 Participants	4 Participants	2 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: 2 weeks or less	0 Participants	0 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: 3 weeks or less	0 Participants	0 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling-Supraclavicular, Contralateral to Vaccine: > than 4 weeks/still experiencing	2 Participants	4 Participants	2 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: I don't know	2 Participants	3 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Contralateral to Vaccine: Missing	0 Participants	1 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: 48 hours or less	6 Participants	2 Participants	2 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: 1 week or less	2 Participants	4 Participants	6 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: 3 weeks or less	0 Participants	0 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Supraclavicular, Ipsilateral to Vaccine: 4 weeks or less	0 Participants	1 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: 1 week or less	10 Participants	17 Participants	19 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: 4 weeks or less	1 Participants	2 Participants	3 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: More than 4 weeks/still experiencing	3 Participants	10 Participants	3 Participants	1 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: Missing	0 Participants	1 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Ipsilateral to Vaccine: I don't know	4 Participants	5 Participants	3 Participants	2 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: 2 weeks or less	3 Participants	3 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: 3 weeks or less	1 Participants	2 Participants	0 Participants	0 Participants	0 Participants
Duration of Lymph Node Swelling as a Side Effect of mRNA and Non-mRNA Vaccines Duration of LN swelling - Axilla, Contralateral to Vaccine: 4 weeks or less	3 Participants	4 Participants	1 Participants	0 Participants	0 Participants

PRIMARY outcome

Due to the inherent activity of mRNA vaccines and the immune system, as well as the role of the lymph nodes in breast cancer (BC) and in breast cancer-related lymphedema (BCRL), this study analyzed the side effect profile in patients treated for BC and who received up to three doses of the COVID-19 vaccinations \[Moderna, Pfizer\]. A separate analysis is presented on results from participants who received the Johnson \& Johnson (J\&J) vaccine as lymph node swelling is not a listed side effect of this non-mRNA vaccine and only a small proportion of the population received this vaccine.

Outcome measures

Outcome measures
Measure	Vaccinated Breast Cancer Patients Dose 1 [mRNA vaccine - Moderna, Pfizer] n=621 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Dose 2 [mRNA vaccine - Moderna, Pfizer] n=621 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [mRNA vaccine - Moderna, Pfizer] n=469 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients [non-mRNA vaccine - Johnson & Johnson] n=49 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).	Vaccinated Breast Cancer Patients Booster [non-mRNA vaccine - Johnson & Johnson] n=34 Participants Patients who enroll in the trial and decided to get the COVID-19 vaccine will complete surveys to indicate their experiences, side effects, location of vaccination (i.e. right arm, left arm, or leg). This information will be analyzed in conjunction with their breast cancer treatment history and lymphedema measurements. Participants were separated into two different cohorts for analysis, Cohort 1 being those who received an mRNA vaccine for their primary vaccination series (two doses of Moderna or Pfizer) and Cohort 2 being those who received a non-mRNA vaccination for their primary vaccination series (one dose of Johnson \& Johnson).
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Fatigue	265 Participants	368 Participants	208 Participants	21 Participants	10 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Chills	59 Participants	147 Participants	90 Participants	10 Participants	5 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Arm Heaviness	60 Participants	59 Participants	30 Participants	2 Participants	2 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Arm numbness	13 Participants	12 Participants	8 Participants	0 Participants	0 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Bell's Palsy	0 Participants	0 Participants	0 Participants	0 Participants	0 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: None	89 Participants	75 Participants	72 Participants	13 Participants	10 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Injection Site Soreness	472 Participants	473 Participants	328 Participants	31 Participants	19 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Generalized Muscle Soreness	143 Participants	198 Participants	115 Participants	9 Participants	5 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Headache	114 Participants	201 Participants	101 Participants	15 Participants	8 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Joint Pain	58 Participants	108 Participants	59 Participants	8 Participants	4 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Fever	31 Participants	104 Participants	52 Participants	7 Participants	5 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Injection Site Swelling	84 Participants	119 Participants	63 Participants	5 Participants	2 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Arm Swelling	16 Participants	27 Participants	17 Participants	1 Participants	1 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Vomiting	4 Participants	7 Participants	6 Participants	0 Participants	1 Participants
Reported Side Effects of the mRNA and Non-mRNA Vaccines Symptom: Other	27 Participants	34 Participants	27 Participants	1 Participants	0 Participants

PRIMARY outcome

Population: Participants are represented in multiple rows for the duration of separate side effects, so they can be accounted for in more than one row. The discrepancy for the "\[mRNA vaccine Dose 1 - Moderna, Pfizer\] reported side effects" Arm/Group is due to three participants who did not respond to the side effects question for Dose 1, resulting in a total of 529 responses out of 532 participants.