A second booster dose of a COVID-19 mRNA vaccine was found to be safe among adults, according to study results published in The Lancet Respiratory Medicine.
Researchers evaluated the safety profile of a second COVID-19 booster dose using patient data captured from a retrospective cohort study (N=250,000) and a prospective cohort study (N=4698). Participants included in the retrospective study were adults who received a second booster dose of the BNT162b2 vaccine between December 30, 2021, and July 22, 2022. Participants included in the prospective study were adults who received smartwatches designed to continuously monitor several physiologic measures, such as pulse.
Kruskal-Wallis testing was used to compare patients’ pulse rates before and after vaccination, and paired-sample t-testing was used to analyze differences in daily heart rates between receipt of the first and second booster dose. Self-reported adverse events following receipt of the first and second booster doses were also assessed via t-testing.
In the prospective study, participants who received the second booster (n=699) were predominantly women (50.2%) with no comorbidities (58.9%), and the median age was 62 years. Participants included in the retrospective study who received both the first and second booster dose (n=17,814) were predominantly women (50.2%) with comorbidities (60.5%), and the median age was 69 years.
Among participants included in the prospective study, the majority (67%; 95% CI, 64-71) reported no new symptoms after receipt of the second COVID-19 booster dose. The most common symptoms were fatigue, headache, muscle pain, and pharyngitis, most of which resolved within 3 days. Further analysis of these patients showed pulse rates peaked 2 days after vaccination, with a mean difference in pulse of 1.163/min compared with baseline. However, pulse rates returned to baseline levels 6 days after vaccination (0.945/min; P= 0.62).
Among participants included in the retrospective study, no significant differences in the risk for Bell palsy, myocardial infarction, or pericarditis were observed after receipt of the second booster dose. None of the participants reported myocarditis before or after vaccination. Of note, there was a greater risk for lymphadenopathy observed following receipt of the first booster dose when compared with the second booster dose.
Study limitations include the use of commercial-grade smartwatches to monitor pulse and potentially limited generalizability to other populations. The researchers also noted the clinical importance of continuously monitoring pulse has not been fully established.
“[Our findings further highlight the short-term safety of the BNT162b2 second booster dose, as reflected in both our subjective and objective data,” the researchers concluded.
Yechezkel M, Mofaz M, Painsky A, et al. Safety of the fourth COVID-19 bnt162b2 mRNA (second booster) vaccine: a prospective and retrospective cohort study. Lancet Respir Med. Published online November 18, 2022. doi:10.1016/s2213-2600(22)00407-6