According to the largest trial of its kind, three doses of the same COVID-19 vaccination or a mix of different jabs work effectively in preventing infections, even against distinct variations. The findings, which were published in The BMJ, imply that the number of vaccination doses, rather than the combination of vaccine types, appears to be the key to boosting immunity and should help shape future public health decisions. While individual COVID-19 vaccinations are well-known, the efficiency of vaccine combinations is less obvious, especially for certain groups, such as the elderly and those who are immunocompromised, according to the researchers.
Despite a quick drop in COVID-19 infections and deaths, they stated it’s critical to determine which vaccination combinations are most effective due to worries about diminishing vaccine immunity and novel variations. From March 8, 2022, researchers from the Chinese University of Hong Kong (CUHK) combed through 38 WHO COVID-19 databases for published studies and preprints on a weekly basis. They found 53 studies with over 100 million people that used 24 different COVID-19 vaccine regimens and seven distinct vaccine types for analysis. “While a three-dose mRNA regimen appears to be the most successful in avoiding COVID-19 infections, any heterologous or homologous three-dose regimen works comparably well in preventing COVID-19 infections, even against various variations,” the researchers wrote.
A homologous regimen consists of three doses of the same vaccination, whereas a heterologous regimen consists of a third dosage that differs from the initial shots. Three doses of either mRNA vaccine appear to be most effective (96%) against non-severe COVID-19 infections and most effective (95%) in lowering COVID-19-related hospital admissions, according to the researchers. They also found that using an mRNA booster after two doses of adenovirus vector vaccines has a good efficacy of 88%. According to the researchers, any three-dose regimen — heterologous or homologous — generates stronger immunity in all age groups, including the over-65s, than a two-dose homologous regimen.
According to them, a third booster dose is required to avoid infection caused by the Omicron form. According to the study, in immunocompromised individuals, a third mRNA booster dose, given as part of a heterologous or homologous protocol, significantly enhances protection over two doses. The effectiveness of three dose immunisation regimens against COVIOD-19-related death, however, remains unknown, according to the data.
These are statistical assessments of findings from observational studies and randomised controlled trials.
Due to a lack of data, the researchers were unable to determine the optimal time interval for prime boost or boosting regimens.