COVID-19 mRNA vaccines are less effective against omicron infections than other variants. A study published in the open access journal “PLOS Medicine” by Margaret L. Lind, of the Yale School of Public Health (United States) and colleagues, suggests that the additional protection offered …
COVID-19 mRNA vaccines are less effective against omicron infections than other variants. A study published in the open access journal ‘PLOS Medicine’ by Margaret L. Lindof the Yale School of Public Health (USA) and colleagues, suggests that the additional protection offered by the initial booster vaccine may be reduced among people with a previous COVID-19 infection.
Evidence indicates that primary vaccination (two doses) and original mRNA booster (third dose) significantly reduce the risk of omicron infection and serious outcomes in the general population, but the benefit of vaccination with COVID-19 mRNA in people who have previously experienced the infection remains unclear.
To estimate the effectiveness of mRNA vaccination against omicron infection among people with a documented prior infection, the researchers conducted a negative case control study using medical records obtained through a COVID study. at least one test for SARS-CoV-2 in Yale New Haven Health System electronic health records.
The study group 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 during the same study period.
Next, the researchers estimated the effectiveness of the vaccine against the infection and, moreover, whether an original booster dose was associated with greater protection beyond the primary vaccination. To do this, the chances of infection were compared between vaccinated people and those likely to receive the booster dose with and without a documented previous infection.
The researchers found that primary vaccination provided protection against omicron infection among people with and without documented prior infection. Although the original booster vaccination was associated with additional protection against omicron infection in people with no prior documented infection, it was not found to be associated with additional protection among individuals with prior documented infection.
The researchers point this out while the initial push may not provide additional benefits in preventing omicron infection in some people, it still offers the best protection against serious illness and hospitalizationaccording to previous studies.
This study was limited to omicron infections and should be considered in conjunction with other existing and future studies examining the relative benefits of booster doses against severe COVID-19 disease among people with and without prior infections. Furthermore, this analysis was performed before the distribution of the COVID-19 bivalent booster and the results are limited to the associations between the parental vaccines and omicron infection.
Lind adds that “In this retrospective study, we found that primary mRNA vaccination provides moderate protection against omicron (BA.1 lineage) infection, regardless of infection history. However, the relative benefits of an original booster dose against omicron infection may be influenced by a person’s history of previous SARS-CoV-2 infection.“, he concludes.
