JAMA Internal Medicine · 2021 · 149 citations · 19 references
Veterinary MedicineImmunologyInfectious DiseasesImmunizationVaccine ImmunologyVaccinologyClinical Vaccine TrialsImmunization SchedulesMrna Vaccine TechnologyVaccinationVaccine EffectivenessVaccine EfficacyBooster Dose EffectivenessBooster Dose EfficacyEfficacy Against InfectionMatched Comparison DesignMatched Control GroupOverall Vaccine EffectivenessSars-cov-2 InfectionVaccine Clinical Trial Design
Waning immunity of the BNT162b2 vaccine prompted a nationwide booster campaign in Israel in August 2021, as other countries also began administering third doses. The study aimed to assess the short‑term benefit of a third BNT162b2 dose versus two doses in preventing SARS‑CoV‑2 infection. Using a retrospective case‑control design with test‑negative and matched case‑control approaches on Maccabi Healthcare Services data from 306,710 adults aged 40+ between August and October 2021. The booster was associated with an 86 % reduction in the odds of a positive PCR test (OR 0.14, 95 % CI 0.13–0.15) during 28–65 days post‑vaccination, compared with two doses.
With the evidence of waning immunity of the mRNA vaccine BNT162b2 (Pfizer-BioNTech), a nationwide third-dose (booster) vaccination campaign was initiated in Israel during August 2021; other countries have begun to administer a booster shot as well.To evaluate the initial short-term additional benefit of a 3-dose vs a 2-dose regimen against infection of SARS-CoV-2.This preliminary retrospective case-control study used 2 complementary approaches: a test-negative design and a matched case-control design. Participants were included from the national centralized database of Maccabi Healthcare Services, an Israeli healthcare maintenance organization covering 2.5 million members. Data were collected between March 1, 2020, and October 4, 2021, and analyses focused on the period from August 1, 2021, to October 4, 2021, because the booster dose was widely administered from August 1 onward.Either 2 doses or 3 doses of the BNT162b2 vaccine.The reduction in the odds of a positive SARS-CoV-2 polymerase chain reaction (PCR) test at different time intervals following receipt of the booster dose (0-6, 7-13, 14-20, 21-27, and 28-65 days) compared with receiving only 2 doses.The study population included 306 710 members of Maccabi Healthcare Services who were 40 years and older (55% female) and received either 2 or 3 doses of the BNT162b2 vaccine and did not have a positive PCR test result for SARS-CoV-2 prior to the start of the follow-up period. During this period, there were 500 232 PCR tests performed, 227 380 among those who received 2 doses and 272 852 among those who received 3 doses, with 14 989 (6.6%) and 4941 (1.8%) positive test results in each group, respectively. Comparing those who received a booster and those who received 2 doses, there was an estimated odds ratio of 0.14 (95% CI, 0.13-0.15) 28 to 65 days following receipt of the booster (86% reduction in the odds of testing positive for SARS-CoV-2).Previous studies have demonstrated that vaccine-derived protection against SARS-CoV-2 wanes over time. In this case-control analysis, we showed an association between receipt of the booster dose and a reduction in the odds of testing positive for SARS-CoV-2, potentially counteracting waning immunity in the short term. Further monitoring of data from this population is needed to determine the duration of immunity following the booster.
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