Breakthrough infections are the bane of the world of vaccines; no inoculation, regardless of its effectiveness, can ever stop all infections 100% of the time. The good news is that, when someone who is vaccinated gets a breakthrough infection, the symptoms are almost always much more mild.
Now a new study reinforces the good news about vaccines and breakthrough infections. According to an article published in the journal Clinical Infectious Diseases, fewer than 1 out of 1,000 people who were either vaccinated or had natural immunity required hospitalization if they suffered from a breakthrough infection. The rates of hospitalization between different groups was statistically insignificant: 6 out of every 10,000 vaccinated patients, 3 out of every 10,000 previously infected but unvaccinated people and 1 out of 10,000 among patients who were both previously infected and vaccinated.
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"We found these results to be in line with previous studies, although the interpretation shouldn't necessarily be that natural immunity provides the same protection as vaccination," lead author Dr. Benjamin Pollock, a researcher in the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery, said in a press statement. "Rather, this study found that among our primary care population, both natural immunity and vaccine immunity appeared to lead to very low rates of breakthrough hospitalizations."
Previously, back in September 2021, a study in The Lancet Infectious Diseases journal revealed that, if a patient has been either vaccinated against or previously infected with COVID-19, they are half as likely to develop so-called "long COVID" through a breakthrough infection as someone without that immunity.
To conduct the new study, the researchers looked at the medical data of 106,349 primary care patients at Mayo Clinic in Rochester, Minnesota over a period of time, looking for changes. They only analyzed adult patients who had tested positive for COVID-19 and/or had been vaccinated against COVID-19. It was notable that among this cohort, only 69 required hospitalization due to a breakthrough COVID-19 infection.
The statistics highlight the fact that vaccines are essential even if a person develops a COVID-19 infection after being inoculated. Vaccines have the double benefit of reducing chances of infection and reducing symptom severity if an infection does occur.
Notably, each successive variant has required a re-evaluation of statistics around infectivity and capacity for immunity evasion. Certainly the omicron variant proved better able to evade vaccines that previous strains. While initially omicron infections appeared less severe on average, omicron variant BA.2 has been better at evading vaccinations than other strains.
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