The rates of COVID-19 hospitalizations and deaths from COVID-19 were substantially lower in vaccinated individuals compared with unvaccinated adults until 6 months after their second dose. Vaccine efficacy against these events was found to be at least 80% for Pfizer-BioNTech and at least 75% for AstraZeneca vaccine. However, the vaccine’s effectiveness against SARS-CoV-2 infection wanes, meaning that rates in vaccinated individuals are similar or higher than in unvaccinated individuals 6 months after the second dose. .
Dr Elsie Horne, senior research associate in Health Statistics and Health Data Science at Bristol Medical School: Population Health Science (PHS) and lead author of the study, said: To date, there is limited and conflicting evidence regarding the rate of decline following the second dose of the COVID-19 vaccine, whether it extends to severe COVID-19, and whether vary according to age and clinical severity.”
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“Although we found that the protection against severe COVID-19 provided by two doses of the vaccine diminishes over time, the very high initial protection means that, although weakened, protection remained high for six months after the second dose. This finding was consistent across all adults, including older adults and those at risk for severe COVID-19.”
Professor Jonathan Sterne is in the department of health statistics and epidemiology at Bristol Medical School: PHS, director of the National Institutes of Health and Care Research Bristol Biomedical Research Center (NIHR Bristol BRC) and director of Research Health Data UK (HDR UK) South-West and co-authors, added: “We found that the rate of vaccine degradation was consistent across subgroups defined by degree of severity. age and clinical vulnerability. The continuing study of how long a COVID-19 vaccine remains effective is important for booster vaccination scheduling and targeting.”
The researchers now plan to lead a follow-up study looking at the vaccine’s effectiveness for a year after the second dose and into the era of the Omicron variant. They are also investigating rates of decline in vulnerable clinical subgroups, such as those with chronic kidney disease and cancer.
Source: Eurekalert
