COVID-19 Vaccines Are Effective At Reducing Severe Illness And Hospitalization

New evidence on breakthrough infections indicates people who tested positive for SARS-CoV-2 after 1 or 2 vaccine doses had significantly lower odds of severe disease, hospitalization, or Long COVID than unvaccinated.

  • After two vaccines doses, the odds of hospitalisation were reduced by more than two-thirds and breakthrough infections were almost two times more likely to be completely asymptomatic.
  • The odds of long COVID-19 (symptoms continuing for 28 days or more after testing positive) were also reduced by more than half for people who received two vaccine doses.
  • People over age 60 who were frail or had underlying conditions had higher odds of a breakthrough infection, especially after only one dose.
  • The findings could have implications for health policies around timing between vaccine doses, potential COVID-19 vaccine booster shots, and for continuing personal protective measures, including mask-wearing and social distancing.

People who tested positive for SARS-CoV-2 after one or two vaccine doses had significantly lower odds of severe disease or hospitalisation than unvaccinated people, according to a large-scale study investigating COVID-19 breakthrough infections published in The Lancet Infectious Diseases journal.   Researchers also found that the odds of experiencing long COVID (illness lasting 28 days or more after a positive test) were cut in half for people who received two vaccines doses.

People most vulnerable to a breakthrough infection after their first vaccine dose included frail older adults (60 years and older), and older adults living with underlying conditions such as obesity, heart disease, kidney disease, and lung disease. In all age groups, people living in deprived areas, such as densely populated urban settings, were more likely to experience a breakthrough infection. These factors were most significantly associated with a post-vaccination infection after receiving the first vaccine dose and before receiving a second dose.

“We are at a critical point in the pandemic as we see cases rising worldwide due to the delta variant. Breakthrough infections are expected and don’t diminish the fact that these vaccines are doing exactly what they were designed to do—save lives and prevent serious illness. Other research has shown a mortality rate as high as 27% for hospitalised COVID-19 patients.

We can greatly reduce that number by keeping people out of the hospital in the first place through vaccination. Our findings highlight the crucial role vaccines play in larger efforts to prevent COVID-19 infections, which should still include other personal protective measures such as mask-wearing, frequent testing, and social distancing,” says study co-lead author Dr Claire Steves of King’s College London, UK. [1]

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