The original, primary booster mRNA vaccine can reduce the risk of infection associated with Omicron

mRNA COVID-19 vaccines are less effective against Omicron infection than other variants. Study published on December 1.Street In Open Access Journal PLOS medicine By Margaret L. Lind of the Yale School of Public Health in the US and colleagues suggest that the additional protection provided by the initial booster shot may be reduced among people with a previous infection with COVID-19.

Evidence suggests that primary vaccination (two doses) and original mRNA vaccination (third dose) significantly reduce the risk of Omicron-associated infections and severe outcomes in the general population. However, the benefit of the mRNA COVID-19 vaccine for people who have previously had the infection remains unclear.

In order to estimate the efficacy of the mRNA vaccine against Omicron infection among subjects with previously documented infection, researchers conducted a test-negative case study using health records obtained through the COVID-19 study of vaccine-eligible subjects over five years of age with at least a SARS-test. CoV-2 in Yale New Haven Health System electronic medical records.

The study cohort included 11,307 people who tested positive for SARS-CoV-2 between November 1, 2021 and April 30, 2022 as well as 130,041 control cases who tested negative in the same time period. The researchers then estimated the vaccine’s efficacy against infection as well as whether the original booster dose was associated with increased protection after the initial vaccination. This was achieved by comparing the odds of injury between booster and booster eligible subjects with or without a documented prior injury.

The researchers found that primary vaccination provides protection against Omicron infection among people with or without a documented prior infection. While the original booster vaccination was associated with additional protection against Omicron infection in subjects without a documented prior infection, it was not found to be associated with additional protection among subjects with a documented prior infection.

The researchers stress that while the initial booster may not provide additional benefits in preventing Omicron infection in some people, it still provides the best protection against severe illness and hospitalization, according to previous studies. This study was limited to Omicron infection and should be considered in conjunction with other current and prospective studies investigating the relative benefits of booster doses against severe COVID-19 disease among people with or without a previous infection. In addition, this analysis was performed prior to the distribution of the bivalent COVID-19 booster and results are limited to associations between the original vaccines and Omicron infection.

In this retrospective study, we found that primary mRNA vaccine provided moderate protection against Omicron infection (strain BA.1) regardless of previous infection history. However, the relative benefits of the original booster dose against Omicron infection may be affected by a person’s history of prior infection with SARS-CoV-2.”

Margaret L. Lind, Yale School of Public Health


Journal reference:

lind, ml, et al. (2022) Association between primary or booster vaccination for COVID-19 mRNA and Omicron BA.1 SARS-CoV-2 strain in previously infected SARS-CoV-2-infected subjects: a negative test-and-trace analysis. PLOS medicine.

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