Full Vaccination Halves Long Covid Risk, Reduces Severity Of Breakthrough Infections: UK Study 

A new study published in The Lancet Infectious Diseases confirms the effectiveness of Covid vaccines at reducing the risk of hospitaisation even in people who received just one dose

Coronavirus testing | File Image

New Delhi: Covid-19 vaccines are effective at reducing severe illnesses that require hospitalisation, and breakthrough infections are almost two times more likely to be completely asymptomatic after two doses, a new study has found. 

The occurrence of SARS-CoV-2 infection after vaccination is described as a breakthrough infection. The study highlights the characteristics of the disease occurring post-vaccination and says the chances of hospitalisation are reduced by more than two-thirds after two shots of any of the Covid vaccines.

The large-scale study, conducted by researchers from several universities in the United Kingdom, has been published in The Lancet Infectious Diseases journal.

The researchers also found that the odds of experiencing long Covid — the condition when the illness lasts 28 days or more after a positive test — were reduced to half for people who have got two doses. 

The study was conducted on UK users of the ZOE Covid study app.

The report, however, noted that since the data obtained from the app was self-reported, the comorbidities, vaccination status, and test results could be inaccurate, and there might have been an underrepresentation of the people living in deprived regions. 

Fewer That 0.2% Tested Positive After Second Shot

The study was conducted between December 8, 2020, and July 4, 2021, and the participants reported their status of Covid-19 infection and vaccination through the ZOE app as part of the UK Covid Symptom Study. 

As many as 12,40,009 users reported that they had received the first vaccine dose, and 6,030 of them, or fewer than 0.5 percent, tested positive for SARS-CoV-2 (cases 1) later. As many as 9,71,504 users reported to have taken the second dose, and 2,370, or less than 0.2 percent, tested positive for Covid-19 (cases 2). More than 1.2 million adults had received at least one dose of either Pfizer-BioNTech, Oxford-Astrazeneca, or Moderna vaccine.

The chances of breakthrough infection being asymptomatic increased by 63 percent after the first vaccine dose, and by 94 percent after the second dose. 

The odds of experiencing long Covid were reduced to 50 percent in people who had received both doses. Also, chances of having severe disease, that is to suffer from five or more symptoms in the first week of illness, were reduced by 70 percent.

Frail older adults (60 years and older) were among those most vulnerable to breakthrough infection after the first dose. Other vulnerable people were the adults with underlying health conditions like kidney disease, heart disease, obesity, and lung disease. Living in deprived regions, including densely populated urban areas, was a common factor in all age groups determining a greater likelihood to experience breakthrough infection. 

‘Vaccines Are Doing Exactly What They Were Designed To Do — Save Lives’ 

The virus was more likely to spread in communities with overall low vaccination rates and having closer living quarters. These factors were mostly related to cases of breakthrough infection after getting the first shot, and before receiving the second dose.

Unvaccinated people suffered from fatigue, cough, fever, and loss of taste and smell more frequently than those who received at least one dose of vaccination.

Dr. Claire Steves of King's College London, UK, one of the lead authors of the study, said: "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 do—save lives and prevent serious illness.” 

She added: “Other research has shown a mortality rate as high as 27% for hospitalised 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.”

Study co-author Dr. Ross Penfold said the older age groups who are frail and are living in care homes, the people living in deprived conditions, and the people with underlying health conditions were at a greater risk of exposure and showed more vulnerability to infection from SARS-CoV-2. 

These groups should be prioritized and must be informed about the timing between the first and second dose and potential booster doses, with the help of specially designed health policies, the statement said.