Breakthrough Covid-19 Infections Despite Vaccination See Red
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People who tested positive for covid-19 after one or two doses of Covishield, Moderna or Pfizer vaccines were less prone to severe disease or hospitalisation than unvaccinated people, a fresh study has reaffirmed.

The large-scale study, showed that after two doses, chances 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, when symptoms last for 28 days or more after testing positive, were also reduced by more than half for people who received two doses, it found.

People most vulnerable to a breakthrough infection after their first vaccine dose included frail older adults--60 years and older--and older adults 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.

Using self-reported data from the UK COVID Symptom Study, through the ZOE app, from 8 December 2020 through 4 July 2021, researchers found that of more than 1.2 million adults who received at least one dose of either the Pfizer-BioNTech, Oxford-AstraZeneca, also known as Covishield in India, or the Moderna vaccine, fewer than 0.5% reported a breakthrough infection more than 14 days after their first dose.

Among adults who received two vaccine doses, fewer than 0.2% experienced a breakthrough infection more than seven days after their second dose. Among those who did experience a breakthrough infection, the odds of that infection being asymptomatic rose 63% after one dose and 94% after the second dose. Researchers also found that the odds of hospitalisation were reduced by approximately 70% after one or two doses, and chances of experiencing severe disease, defined as having five or more symptoms in the first week of illness, fell by approximately one-third. In addition, the odds of long COVID halved 50% after two doses.

For those who did experience symptoms after either one or two vaccine doses, such as fatigue, cough, fever, and loss of taste and smell, almost all symptoms were reported less frequently than in unvaccinated people. The authors noted some limitations of the study. The research uses self-reported data and therefore the reported comorbidities, test results, and vaccination status could be inaccurate or incomplete, and individuals living in more deprived areas could be underrepresented.