Booster Vaccination to Reduce SARS-CoV-2 Transmission and Infection

Abstract

The vaccines to prevent COVID-19 are remarkable for their safety, efficacy, and pace of development. Initial enthusiasm that followed the release of the preliminary results that formed the basis for distribution of the vaccines under Emergency Use Authorization (EUA) has been dampened by the inequity in access to the vaccines across the globe, vaccine hesitancy, and emergence of variants that partly evade vaccine-induced antibodies. These factors are related, and all 3 contribute to ongoing morbidity, mortality, and societal disruption related to SARS-CoV-2 in much of the world. Incomplete coverage with the vaccine leads to infection of immunocompromised persons who are likely to harbor the virus for prolonged periods (or chronically), allowing for mutations that are then selected for immune evasion and better fitness to the human host. 1 The new variants are sufficiently altered structurally such that neither prior SARS-CoV-2 infection or even much higher levels of vaccine-induced antibodies are protective.In this issue of JAMA, Spitzer and colleagues assess the effect of a booster dose of the mRNA vaccine BNT162b2 (Pfizer-BioNTech) on acquisition of SARS-CoV-2 infection among health care workers in a tertiary medical center in Tel Aviv, Israel. 2 Israel achieved high vaccination coverage of most health care workers, who were prioritized for immunization receiving both doses of the BNT162b2 vaccine by the end of January 2021. As such, when the Delta variant arose in June 2021, most health care workers had received their second dose of vaccine about 6 months earlier, and emerging data showed that the antibody titers in response to vaccination had waned.Although Spitzer et al initially aimed to provide a booster vaccine dose only for persons with antibody titers less than the median, universal boosting was recommended by health authorities. The investigators enrolled a cohort of health care workers who had completed a 2-dose vaccination series of BNT162b2 and subsequently received a booster dose of the vaccine. Infections in the cohort were monitored by SARS-CoV-2 polymerase chain reaction (PCR) tests every 2 weeks regardless of symptoms. Anti-SARS-CoV-2 spike protein receptorbinding domain (anti-S1-RBD) was measured at baseline and 1 month after the booster.The study cohort included 1928 health workers, and 1650 (85.6%) received a booster dose during the study. The median overall follow-up was 39 days, and the median follow-up of boosted persons, beginning 7 or more days after the receipt of the booster vaccination, was 26 days. Overall, 3552 PCR tests were obtained with 51% before and 49% after boosting. A total of 44 persons tested positive for SARS-CoV-2 during

SARS-CoV-2 Spike and Neutralizing Antibody Kinetics 90 Days after Three Doses of BNT162b2 mRNA COVID-19 Vaccine in Singapore

“…The interval between vaccine doses may affect the resulting antibody response. Some studies recommend a longer interval to establish a more durable response and more time to develop long-term immunity [25]. In one study [5], geometric mean responses were compared between groups of patients who were boosted at 186 versus 262 days post-second dose (Comirnaty vaccine); peak post-booster antibody geometric mean responses 2-4 weeks post-booster were higher in the extended dosing interval group (geometric mean titers 13,980 versus 18,104).…”

A Macro-Level Association of Vaccination Rate with the Number of Confirmed COVID-19 Cases in the United States and Japan

“…Previous studies also showed that the viral lord declined more rapidly in vaccinated people than in unvaccinated people [ 40 , 41 ]. As viral load can be a proxy for infectiousness, vaccination may be effective in reducing the transmission of SARS-CoV-2 infections [ 42 ]. Moreover, from the viewpoint of multilevel analysis, the effects on individual-level outcomes can be divided into individual-level and group-level factors [ 43 , 44 ].…”

SARS‐CoV‐2 variants and vulnerability at the global level

“… 79 , 124 S‐glycoprotein mutations may influence transmission kinetics and the possibility of immunological escape. 125 Vaccination decreases the incidence of delta variant infection and speeds up viral clearance, according to several studies. 119 Despite this, fully vaccinated persons with breakthrough infections have peak viral loads comparable with unprotected patients and may easily spread illness in home settings, including completely vaccinated contacts.…”