A previous Covid infection provided protection more “durable” against infection with the Omicron variant than two or three doses of Pfizer or Moderna vaccines — but protection was stronger after vaccination and a previous infection, according to a study published in New England Journal of Medicine on Wednesday (15), highlighting the benefits of vaccination for all amid a new increase in cases.
A previous Covid infection halved the risk of symptomatic reinfection with Ômicron, according to the peer-reviewed study, which analyzed health data covering the entire population of Qatar (2.9 million people) between December 2021 and February 2022.
Protection against reinfection was “moderate and durable,” the researchers said, and the result was approximately the same for Omicron subvariants BA.1 and BA.2. Protection after vaccination disappeared “rapidly”, the researchers said, and was “negligible” after primary vaccination (two doses of Pfizer or Moderna mRNA vaccine) and about 60% after booster, although the researchers noted that most of the people studied had taken the second dose more than six months ago and the third dose within the last 45 days.
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Hybrid immunity after vaccination and infection offered the best protection against reinfection, by approximately 50% after primary vaccination and nearly 80% after booster. The findings underscore the “benefit of vaccination” even for those with a previous infection. While protection varied significantly, the researchers emphasized that prior infection, vaccination, and hybrid immunity conveyed an equally high degree of protection — around 70 percent — against serious or fatal illness.
The finding is in line with a growing body of research that illuminates the strong protective benefits that come after vaccination and infection. She highlights the benefits of getting vaccinated even if you have already had Covid-19. It also underscores the transient nature of some aspects of vaccine-derived protection, which has become particularly noticeable as the highly infectious Omicron variant has emerged worldwide, regardless of vaccine coverage.
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Experts do not fully understand why natural infection provides more durable immunity, and it is possible that this will change depending on which variant a person is infected with. This study would also cover people infected with variants that were prevalent before the wave of Omicron hit Qatar.
Scientists and public health officials are now trying to understand how to reproduce this more durable natural immunity as they prepare the next generation of vaccines for early booster campaigns and face a new wave of Omicron subvariants – BA.4 and BA.5 – that are gaining ground. in the United States and Europe. Evidence suggests that, unlike earlier variants, infection with Omicron may not provide much protection against subsequent infections.
The researchers observed that the degree of protection of hybrid immunity after booster it appeared to have two separate layers, as if protection against infection and vaccination acted independently rather than synergistically or through a similar mechanism. This was also observed among people who had been infected before and vaccinated but not given a booster dose, and who had a similar level of protection to people who had just had a past infection (suggesting that protection from primary vaccination diminished over time. ). The “impressive” finding “needs to be further investigated” to better understand how the two forms of immunity interact, the researchers added.