Individuals who are vaccinated for Covid-19 and experience breakthrough infections are 50% less likely to have long Covid symptoms that last for a month or longer, according to observational findings from the ongoing Covid Symptom Study. Results from this study are detailed in this article that was originally published Sept. 2, 2021. Click here to read the original article and obtain CME/CE credit for the activity.
Compared to unvaccinated people with Covid-19, fully vaccinated people who experienced breakthrough infections were about half as likely to have long Covid symptoms lasting more than a month, new research found.
The observational findings were based on data from the ongoing Covid Symptom Study, involving more than 1.2 million people in the United Kingdom and including more than 8,000 who tested positive for SARS-CoV-2 after receiving a first or second dose of either the BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) mRNA vaccines or the ChAdOx1 nCoV-19 (Oxford/AstraZeneca) double-stranded DNA vaccine.
Older age and frailty were associated with an increased risk for post-vaccination infection and worse outcomes following a first vaccination dose in people with breakthrough infections. However, fully vaccinated older adults with breakthrough infections were also more likely than unvaccinated controls to be asymptomatic.
Most Covid-19 symptoms were less common in the vaccinated versus unvaccinated participants who became infected.
The Covid Symptom Study is among the first to characterize Covid-19 symptoms associated with post-vaccination breakthrough infections. Study findings were published online Sept. 1 in the journal Lancet Infectious Diseases.
“Our results are relevant for health policies post-vaccination and highlight the need to balance personal protective measures in those at risk of post-vaccination infection with the adverse effects from ongoing social restrictions,” wrote researcher Michela Antonelli, PhD, of King’s College London, and colleagues.
The researchers added that prioritizing booster vaccinations and optimizing infection control measures for those at greatest risk, such as the frail elderly, may be needed moving forward.
“Fully vaccinated individuals with Covid-19, especially if they were 60 years or older, were more likely to be completely asymptomatic than were unvaccinated controls,” Antonelli and colleagues wrote. “This finding might support caution around relaxing physical distancing and other personal protective measures in the post-vaccination era, particularly around frail older adults and individuals living in more deprived areas, even if these individuals are vaccinated.”
The Covid Symptom Study includes volunteers who self-report data through a mobile app on Covid-19 tests, symptoms, vaccination status, and other information relevant to better understanding Covid-19.
Cases in the newly published risk-factor analysis received a first or second dose of a Covid-19 vaccine between early December 2020, and early July 2021, and had either a positive Covid-19 test at least 14 days after their first vaccination (but before their second; cases 1) or a positive test at least 7 days after their second vaccination (cases 2).
The cases were compared to various control groups, including vaccinated people without breakthrough infections and unvaccinated people.
A total of 1.24 million Covid Symptom Study app users reported a first vaccine dose during the study period, of whom 6,030 (0.5%) subsequently tested positive for SARS-CoV-2 (cases 1). A total of 975,504 reported a second dose, of whom 2,370 (0.2%) subsequently tested positive for SARS-CoV-2 (cases 2).
In the risk factor analysis:
- Frailty was associated with post-vaccination infection in older adults (≥60 years) after their first vaccine dose (odds ratio [OR] 1.93, 95% CI 1.50–2.48; P<0.0001).
- People living in highly deprived areas had an increased odds of post-vaccination infection following their first vaccine dose (OR 1.11, 95% CI 1.01–1.23; P=0.039).
- People who were not obese (BMI <30 kg/m²) had lower odds of infection following their first vaccine dose (OR 0.84, 95% CI 0.75–0.94; P=0.0030).
Vaccination (compared with no vaccination) was associated with reduced odds of hospitalization or having more than five symptoms in the first week of illness following the first or second dose, and long-duration (≥28 days) symptoms following the second dose.
The researchers noted that the observation that asymptomatic and minimally symptomatic infection is common in partially or fully vaccinated people highlights the importance of continued testing for SARS-CoV-2 testing after vaccination to protect vulnerable populations.
Study limitations included the self-reported nature of the study, the under-representation of people living in poverty, and the inability to analyze the impact of ethnicity given the low use of the reporting app by minorities.
“Our findings might support caution around relaxing physical distancing and other personal protective measures in the post-vaccination era, particularly around frail older adults and individuals living in more deprived areas, even if these individuals are vaccinated, and might have implications for strategies such as booster vaccinations,” Antonelli and colleagues wrote.
Salynn Boyles, Contributing Writer, BreakingMED™
This research was funded by ZOE, the UK Government Department of Health and Social Care, the Wellcome Trust, the UK Engineering and Physical Sciences Research Council, UK Research and Innovation and Artificial Intelligence Center for Value Based Healthcare and others.
Several researchers were employees of ZOE during the conduct of the study.
Cat ID: 31
Topic ID: 79,31,730,933,31,520,926,192,561,927,925,934
