Amid questions of the long-term effectiveness of COVID-19 vaccines, a study whose results were published Wednesday in The Lancet showed that the chance of contracting the virus after being fully vaccinated is extremely rare.
The study of more than one million adults in the United Kingdom also found that vaccines cut in half the risk of long covid, a condition in which the symptoms of COVID-19 linger for months.
Participants in the study included those who had been partially or fully vaccinated between December 2020 and July 2021 with either the Pfizer-BioNTech, Moderna or Oxford-AstraZeneca vaccine.
According to the studys results, only 0.5% of the participants reported contracting the virus after the first dose of a vaccine. Those cases are known as breakthrough infections.
Fourteen days after the second dose of a vaccine, when a person is considered fully vaccinated, the breakthrough rate fell to less than 0.2%.
We are at a critical point in the pandemic as we see cases rising worldwide due to the delta variant, the studys co-lead author Dr. Claire Steves said.
Breakthrough infections are expected and dont diminish the fact that these vaccines are doing exactly what they were designed to do save lives and prevent serious illness.
For those who did contract the virus after being fully vaccinated, 94% had no symptoms of the disease. For those who had received only one dose of a two-dose vaccine, the likelihood of being without symptoms after contracting the virus was 63%.
The study also showed that those age 60 or older who were vaccinated but still contracted the virus were much less likely to have any COVID-19 symptoms.
According to the study, the finding might support caution around relaxing physical distancing and other personal protective measures in the post-vaccination era, particularly around frail older adults.
The studys authors noted that the data used was self-reported by the participants, and the total number of participants included a majority of women.
On Monday, during a presentation to the CDCS Advisory Committee on Immunization Practices, Dr. Sara Oliver said that the effectiveness of the vaccines to prevent hospitalization ranged from 75% to 95%.
According to Oliver, the vaccines ability to prevent a COVID-19 infection ranged from 39% to 84% since the Delta variant became the dominant version of the virus.
Vaccines remain effective in preventing hospitalization and severe disease but might be less effective in preventing infection or milder symptomatic illness, Oliver said in the presentation.