The largest medical study on vaccines against the coronavirus has revealed the "ideal" number of doses for preventing infection from the disease that has spread globally. According to the study conducted by The Chinese University of Hong Kong and published in the British Medical Journal, which included 100 million people, three doses of the same "COVID-19" vaccine or a mix of different vaccinations effectively protect against the pandemic.
The study, based on data from 38 global health organizations, indicated that the three doses also work against various COVID variants. The researchers noted that "despite the rapid decline in infections and deaths from the coronavirus, concerns about reduced vaccine effectiveness and new variants make it essential to understand the most successful vaccine combinations," as reported by the British newspaper "The Guardian."
The study defined receiving three doses of the same vaccine as the homogenous regimen, while receiving a third dose that differs from the two initial doses was termed as the heterogeneous regimen. Upon analyzing the results, researchers found that three doses of any vaccine based on mRNA technology, such as "Pfizer" and "Moderna," appeared to be 96% effective against non-severe "COVID-19" infections and 95% effective in reducing hospital admissions.
The results also showed that any system of three doses—whether heterogeneous or homogenous—elicited a higher immune response across all age groups compared to the two-dose homogenous regimen. It was found that "for patients with immunocompromised conditions, a third booster dose, as part of a heterogeneous or homogenous regimen, also significantly enhances protection compared to just two doses."
The study's authors acknowledged that more research is needed as they did not evaluate the optimal interval between the primary doses and the booster shot.
