Three doses of mRNA vaccines – even a mixture of vaccines — provide 96% effectiveness against non-severe COVID infections and 95% effectiveness against COVID-related hospitalization, the study published in the British Medical Journal says.
“An mRNA booster is recommended to supplement any primary vaccine course,” the study concluded “Heterologous and homologous three dose regimens work comparably well in preventing covid-19 infections, even against different variants.”
A homologous regimen means three doses of the same vaccine are given. A heterologous regimen means the third dose differs from the first two doses.
A research team from the Chinese University of Hong Kong looked at 38 World Health Organization Covid-19 databases starting on March 8, 2022, and found 53 studies involving more than 100 million participants. The participants received seven different types of vaccine and 24 combinations of vaccine courses.
Researchers said they had “low certainty” about how vaccines will work against Omicron variants because relevant studies were conducted during the omicron outbreak.
“However, we are confident that a three-dose regimen will effectively prevent COVID-19 variants. The results have consistently shown a considerable reduction in COVID-19 infections across different variants, despite the studies conducted during the peak of infections.”
The study did not conclude whether three doses were effective in reducing the risk of death by COVID