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COVID-19 vaccine helps protect against severe infection long-term, study finds

Experts say different vaccine types may yield different levels of protection

COVID-19 vaccine concept
Photo (c) Joao Paulo Burini - Getty Images
A new study conducted by researchers from Umea University explored the efficacy of the COVID-19 vaccine long-term. They learned that while protection from the virus may start to wane at around seven months post-vaccination, the shot was effective at protecting consumers from serious infection

“The bad news is that the protection against infection seems to be diminished by seven months after the second dose of the vaccine,” said researcher Peter Nordström. “The good news, however, is that the protection against severe infection that leads to hospitalization or death seems to be better maintained. Vaccination is therefore very wise and important.” 

Preventing serious infection

For the study, the researchers analyzed data from people enrolled in the Public Health Agency of Sweden. They looked at those who had received the Pfizer, Moderna, and AstraZeneca COVID-19 vaccines and compared their infection status up to nine months after full vaccination with those who hadn’t been vaccinated against COVID-19. In a second analysis, they evaluated the severity of COVID-19 infections related to vaccination status. 

Overall, the study showed that protection against COVID-19 got weaker over time. However, it varied with each vaccine type. Six months after the second dose of Moderna, participants were roughly 60% protected from infection; they were nearly 30% protected six months after the second dose of Pfizer. 

More importantly, the vaccines proved to be more effective at preventing severe cases of COVID-19. Participants were nearly 90% less likely to contract severe cases of COVID-19 within one month of vaccination and nearly 65% less likely to develop a severe infection between four and nine months post-vaccination.

The researchers also learned that older consumers may be more vulnerable to infection, regardless of what type of vaccination they received or how much time had passed since vaccination. 

“The results underscore and support the decision to offer a third dose,” said researcher Marcel Ballin. “In particular, the results show that it was correct to prioritize the oldest and frailest individuals.” 

Moving forward, the researchers hope their findings will influence public health strategies regarding the booster shot – especially for those who have the highest risk of contracting COVID-19. 

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