A letter to the editor from researchers affiliated with Hadassah Hebrew University Medical Center (HHUMC) in Jerusalem investigated efficacy of the BNT162b2 vaccine among HHUMC health care workers. They discusses how 689 out of 6680 (10.3%) workers had been infected with COVID-19 through January 31, 2021, similar to the overall rates in Jerusalem which has the highest COVID-19 incidence in Israel. The trend in weekly incidence of COVID-19 decreased dramatically and remained low after 4 weeks (Table 1) despite the B.1.1.7 variant surge in up to 80% of cases. These findings suggest the effectiveness of the BNT162b2 vaccine among high-incidence areas and against variants.

A retrospective cohort study conducted at St. Jude Children's Research Hospital analyzing 5217 workers from December 17, 2020 to March 20, 2021 by a bio-statistician found that the incidence rate ratio—the ratio of diagnosed cases per person-days of follow-up in vaccinated compared with unvaccinated groups—steadily decreased in participants receiving both one and two doses of the BNT162b2 (Pfizer-BioNTech) vaccine (Table 1). They also reported lower cumulative incidence of asymptomatic screening positive test results and symptoms (Figure 1), but the study design and unequal follow-up schedules warrant future studies.

*One author reported serving as a consultant to Pfizer and another reported serving on advisory boards for Roche Molecular, Quidel Corporation, and Inflammatix outside the submitted work.

In a letter to the editor, researchers associated with UCSD and UCLA health systems discuss SARS-CoV-2 infection rates in vaccinated healthcare workers in California. 36,659 healthcare workers received the first vaccine dose, 28,184 received the second dose, and 379 vaccinated healthcare workers tested positive at least 1 day after vaccination (Table 1). Vaccinated healthcare workers at UCSD had a 1.19% absolute risk of testing positive for SARS-CoV-2, while those at UCLA had a 0.97% risk. These results suggest the high efficacy of the Pfizer and Moderna vaccines.

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Researchers from South Africa conducted a multicenter, randomized, placebo-controlled trial enrolling 6324 participants between August 17, 2020-November 25, 2020 to assess the efficacy and safety of NVX-CoV2373 vaccine against the B.1.351 SARS-CoV-2 variant. They found 49.4% overall vaccine efficacy and 60.1% in HIV-negative participants. Genome sequencing showed 38 out of 41 COVID-19 cases were caused by the B.1.351 variant (Figure 1, 2), and post hoc analysis showed 51% efficacy among HIV-negative participants against B.1.351. Safety analysis revealed higher reactogenicity in the vaccine group than the placebo group and few adverse events in either group, suggesting the NVX-CoV2373 vaccine is safe and effective against the B.1.351 SARS-CoV-2 variant.