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Course: Analysis of COVID-19 Incidence and Severity Among Adults Vaccinated With 2-Dose mRNA COVID-19 or Inactivated SARS-CoV-2 Vaccines With and Without Boosters in Singapore

CME Credits: 1.00

Released: 2022-08-26

Key Points

Question What is the rate and severity of COVID-19 in adult recipients of 2 or 3 doses of mRNA or inactivated SARS-CoV-2 vaccines?
Findings In this cohort study including 2,441,581 individuals aged 30 years or more, the estimated effectiveness of the mRNA booster against Omicron-confirmed infections ranged from 31.7% to 41.3% with rapid waning over time. Estimated mRNA booster effectiveness against severe COVID-19 was 87.4% with no evidence of waning up to 6 months after boosting, while the estimated 3-dose inactivated SARS-CoV-2 booster effectiveness against severe COVID-19 was 69.6%.
Meaning These results suggest that booster mRNA vaccine protection was durable against severe COVID-19 over 6 months regardless of vaccine combination, and 3-dose inactivated SARS-CoV-2 vaccination provided greater protection than 2-dose inactivated SARS-COV-2 vaccine but less protection compared with 3-dose mRNA.

Abstract

Importance Assessing booster effectiveness of COVID-19 mRNA vaccine and inactivated SARS-CoV-2 vaccine over longer time intervals and in response to any further SARS-CoV-2 variants is crucial in determining optimal COVID-19 vaccination strategies.
Objective To determine levels of protection against severe COVID-19 and confirmed SARS-CoV-2 infection by types and combinations of vaccine boosters in Singapore during the Omicron wave.
Design, Setting, and Participants This cohort study included Singapore residents aged 30 years or more vaccinated with either at least 2 doses of mRNA COVID-19 vaccines (ie, Pfizer-BioNTech BNT162b2 or Moderna mRNA-1273) or inactivated SARS-CoV-2 vaccines (Sinovac CoronaVac or Sinopharm BBIBP-CorV) as of March 10, 2022. Individuals with a known SARS-CoV-2 infection prior to December 27, 2021, an infection on or before the date of their second vaccine dose, or with reinfection cases were excluded.
Exposures Two or 3 doses of Pfizer-BioNTech BNT162b2, Moderna mRNA-1273, Sinovac CoronaVac, or Sinopharm BBIBP-CorV.
Main Outcomes and Measures Notified infections from December 27, 2021, to March 10, 2022, adjusted for age, sex, race, housing status, and calendar days. Estimated booster effectiveness, defined as the relative incidence-rate reduction of severe disease (supplemental oxygen, intensive care, or death) or confirmed infection following 3-dose vaccination compared with 5 months after second mRNA dose, was determined using binomial regression.
Results Among 2,441,581 eligible individuals (1,279,047 [52.4%] women, 846,110 (34.7%) aged 60 years and older), there were 319,943 (13.1%) confirmed SARS-CoV-2 infections, of which 1513 (0.4%) were severe COVID-19 cases. mRNA booster effectiveness against confirmed infection 15 to 60 days after boosting was estimated to range from 31.7% to 41.3% for the 4 boosting combinations (homologous BNT162b2, homologous mRNA-1273, 2-dose BNT162b2/mRNA-1273 booster, and 2-dose mRNA-1273/BNT162b2 booster). Five months and more after boosting, estimated booster effectiveness against confirmed infection waned, ranging from –2.8% to 14.6%. Against severe COVID-19, estimated mRNA booster effectiveness was 87.4% (95% CI, 83.3%-90.5%) 15 to 60 days after boosting and 87.2% (95% CI, 84.2%-89.7%) 5 to 6 months after boosting, with no significant difference comparing vaccine combinations. Booster effectiveness against severe COVID-19 15 days to 330 days after 3-dose inactivated COVID-19 vaccination, regardless of combination, was estimated to be 69.6% (95% CI, 48.7%-81.9%).
Conclusions and Relevance Booster mRNA vaccine protection against severe COVID-19 was estimated to be durable over 6 months. Three-dose inactivated SARS-CoV-2 vaccination provided greater protection than 2-dose but weaker protection compared with 3-dose mRNA.


Educational Objective
To identify the key insights or developments described in this article


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