According to the largest study of its kind, three doses of the same Covid-19 vaccine or a combination of shots work just as well to prevent infections.
Although the effectiveness of individual coronavirus vaccines is well known, the evidence around combinations of blows has been less clear, especially for particular groups such as the elderly and those who are immunocompromised.
Now, a global analysis of data from more than 100 million people confirms that the number of doses is the key to boosting immunity rather than jab combinations. The findings have been published in the BMJ.
According to the study, three doses of the same vaccine or a combination of different types work in a comparable way to prevent Covid-19 infections, even against different variants.
Despite a rapid decline in Covid-19 infections and deaths, concerns about declining vaccine immunity and new variants make it important to understand which vaccine combinations are most effective, the BMJ said.
The Chinese University of Hong Kong (CUHK) searched 38 World Health Organization Covid-19 databases weekly for published and preprinted studies as of March 8, 2022. They identified 53 studies with 100 million of people with 24 combinations of Covid vaccination courses.
Receiving three doses of the same vaccine is known as a homologous regimen, while receiving a third dose that differs from those administered as two primary doses is called a heterologous regimen.
After considering differences in study design and quality, CUHK researchers found that three doses of any mRNA vaccine appear to be the most effective (96%) against non-Covid-19 infections. severe and most effective (95%) to reduce Covid-19. related hospital admissions.
But the results also show that any three-dose regimen, heterologous or homologous, induces higher immunity in all age groups, even those over the age of 65, than a two-dose homologous regimen.
And the study found that in immunocompromised patients, a third dose of mRNA enhancement, as part of a heterologous or homologous regimen, also greatly improves protection compared to two doses.
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The effectiveness of Covid-19-related three-dose vaccine regimens remains uncertain.
The researchers acknowledged some of the limitations of the study, including the fact that they did not evaluate the optimal time interval for boost or gain regimes, due to limited information.
“Reinforcement of mRNA is recommended to complement any primary vaccination course,” the researchers concluded. “Heterologous and homologous three-dose regimens work comparatively to prevent Covid-19 infections, even against different variants.”