Breakthrough infection is common after first vaccine dose among frail older adults (60 years and older), and older adults living with underlying conditions such as obesity, heart disease, kidney disease, and lung disease.
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 dosave lives and prevent serious illness.
Other research has shown a mortality rate as high as 27% for hospitalized 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.
Self-reported data from the UK COVID Symptom Study through the ZOE app from 8 December 2020 through 4 July 2021 enabled researchers to know that 1.2 million adults who received at least one dose of either the BNT162b2 (Pfizer-BioNTech), ChAdOx1 nCoV-19 (Oxford-AstraZeneca), or mRNA-1273 (Moderna) vaccine, fewer than 0.5% reported a breakthrough infection (6,030 positive cases after 1,240,009 first vaccine doses) more than 14 days after their first dose.
Among adults who received two vaccine doses, fewer than 0.2% experienced a breakthrough infection (2,370 positive cases after 971,504 second vaccine doses) more than seven days after their second dose.
The odds of being asymptomatic increased by 63% after one vaccine dose and by 94% after the second dose among breakthrough infection cases.
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.
Limitations:
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.
These findings might not apply to all timepoints post-vaccination, to settings with different proportions of SARS-CoV-2 variants, or to countries with different vaccination schedules.
Source: Medindia
