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Vaccines Slash Risks Of Serious Illness, Hospitalization And Long Covid For Breakthrough Coronavirus Infections, Study Confirms



While not able to prevent all coronavirus infections, Covid-19 vaccines drastically cut the odds of severe illness and hospitalization in rare breakthrough cases, according to a study published in The Lancet Infectious Diseases journal Wednesday, underscoring the benefits of vaccination as hospitals across the country struggle to cope with surges of mostly unvaccinated patients. 

Key Facts

One or two doses of Moderna, Pfizer-BioNTech or AstraZeneca vaccines reduced the chances of hospitalization by around 70%, according to a peer-reviewed analysis of data from roughly 2 million fully or partially vaccinated people in the U.K.

Vaccination also contributed towards roughly 30% lower odds for severe illness, counted as having five or more symptoms in the first week of illness, with fully immunized individuals having slightly lower odds.     

Breakthrough infections were almost twice as likely to be asymptomatic in the fully vaccinated, the researchers found, and these patients were half as likely to develop long Covid, the debilitating, lingering illness that can persist for months or years after infection.

Among the rare Covid-19 cases reported in those getting a shot—fewer than 0.5% of the partially vaccinated and 0.2% of the fully vaccinated in the study did—symptoms were almost always less severe, except for sneezing, which the researchers noted was more common among the partially vaccinated.     

The researchers also found a possible link between age and breakthrough infections, especially among frail adults over the age of 60, who were almost two times as likely to contract Covid-19 after one vaccine dose than healthy older adults. 

People living in deprived areas were also more likely to experience breakthrough infections—mostly after the first dose—though the researchers warned this could be explained by other reasons like living conditions and lower levels of vaccine uptake in the community.       

Key Background 

While vaccines are known to offer protection against Covid-19 after just one dose, the exact nature of this shield in those that do become infected has not been fully elucidated. The researchers describe this study as the “first to investigate” the characteristics of a Covid-19 infection after the first and second shots. The findings offer an insight into why, despite sky high coronavirus levels in the U.S., almost all patients ending up in hospital or dying from the disease are unvaccinated and offers more proof that vaccines are the best protection against Covid-19 even if they are less effective against the delta variant. That older individuals are seemingly at greater risk of breakthrough infections will likely buoy calls for booster shots in wealthy countries. The U.S. plans to provide them from September, a decision that has been criticized by health organizations as unfair and possibly prolonging the pandemic as many countries have hardly administered any vaccines at all. 

What We Don’t Know

There were several limitations to the study. As it was conducted between 8 December 2020 through July 4 2021, it covers several different phases of dominant coronavirus variants in the U.K. (notably the rise, and subsequent fall, of alpha and the delta variant). This makes it harder to draw firm conclusions and findings may not apply to places with other variant mixes, the researchers noted. The U.K. ‘s vaccination schedule—which featured a much longer gap between doses than used in many countries, including the U.S.—could also limit the applicability of the findings elsewhere, the researchers added. Finally, being based on self-reported data from the Zoe Covid study, it’s possible records for some symptoms, vaccination status, test results and other health conditions are inaccurate, though the researchers said the study design has allowed a “good characterisation of infections.”

Further Reading

Risk factors and disease profile of post-vaccination SARS-CoV-2 infection in UK users of the COVID Symptom Study app: a prospective, community-based, nested, case-control study (Lancet)

Delta Variant More Than Doubles Risk Of Covid Hospitalization, U.K. Study Finds (Forbes)

Vaccine Protection Wanes Within Six Months Of Second Covid Shot, Study Warns, But They’re Still Effective Against Delta (Forbes)

Breakthrough Covid Cases: Uncommon and Often Mild, but Not Always (NYT)

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Source: Forbes


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