June 20, 2021 ~ TrialSite News ~

VA Boston Health System Study Indicates One Dose of mRNA-based Vaccine Could Add Full Protection

Recently, TrialSite made a case that growing concerns over mRNA-based COVID-19 vaccine safety may be resolved by reducing the total dosage to one dose. That’s because the data reveals that the one-shot regimen would suffice but the way the efficacy was represented, the two-shot regimen became the apparent necessity. But was that decision based on science or other concerns? Now a recent retrospective cohort study published in JAMA delved into hazard ratios of acquiring SARS-CoV-2 in vaccinated compared with unvaccinated healthcare workers (HCWs). Including 4028 HCWs, 3367 (83.6%) were vaccinated during the study period. The study authors detected SARS-CoV-2 infection in 107 HCWs during the study (39 vaccinated and 68 unvaccinated). Most of the infections were symptomatic (73.5%) and 7 (6.5%) were asymptomatic, which were detected during routine surveillance. The VA Boston Healthcare System-based study team reported, “Among the 39 SARS-COV-2–positive vaccinated HCWs, 26 (66.7%) received dose 1 before December 29, 2020. Vaccine clinical effectiveness was 50.3% (95% CI, 23.0%-67.9%) for the entire 42-day period of follow-up, 77.5% (95% CI, 61.2%-87.0%) for days 8 through 42, and 95.0% (95% CI, 86.0%-98.2%) for days 15 through 42 (Figure). Clinical effectiveness was similar when analysis was limited to the initial 28 days of study, thereby excluding dose 2 effects.” TrialSite includes bold for emphasis. This group observed a first-dose risk reduction of 95% after day 14 and felt it highlights the potential for vaccination with mRNA-1273 to rapidly mitigate surges of vaccine-sensitive SARS-CoV-2 infection in HCWs. This study represents additional evidence that a single dose could have sufficed, lowering adverse events. But a government payment per dose perhaps incentivized a different outcome.

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