Can fully vaccinated people get Covid-19 again? Experts weigh in

People, who have been fully vaccinated against the coronavirus disease (Covid-19), if they do become infected have a milder illness than those who have not been inoculated, several studies in India and abroad have shown. Experts have said that vaccination is key to containing the spread of the pandemic and remains the best protection against severe illness from Covid-19.

Several studies have shown that vaccines are slightly less effective against the Delta variant of coronavirus but they are still highly effective but only after the second dose. Recent data from the UK government shows that full immunisation can offer about 96 per cent protection against hospitalisation and 79 per cent protection against symptomatic infection by the Delta variant. Protection after only one dose, however, is much weaker at 35 per cent, according to the same data.

"One dose is not enough, full vaccination is needed to protect the most vulnerable," a public health notice from the European Centre for Disease Control (ECDC) has also said.

AFP reported citing local American media that Anthony Fauci, the top US infectious disease scientist, called the variant the "greatest threat" to efforts to control the virus and urged for an acceleration in vaccinations.

CDC study

A study by the US Centers for Disease Control and Prevention (CDC), which looked at more than 3,900 essential workers, shows fully vaccinated people are more than 90 per cent protected against infection. According to the ongoing study, even partially vaccinated people are 81 per cent less likely to become infected than people who haven't had been inoculated.

The CDC study finds the mRNA Covid-19 vaccines authorised by the Food and Drug Administration "reduce the risk of infection by 91 percent for fully vaccinated people". "This adds to the growing body of real-world evidence of their effectiveness. Importantly, this study also is among the first to show that mRNA vaccination benefits people who get COVID-19 despite being fully vaccinated (14 or more days after dose 2) or partially vaccinated (14 or more days after dose 1 to 13 days after dose 2)," CDC said in a statement earlier this month.

The study of health care staff, first responders and other frontline essential workers who have been tested weekly since December showed that so far 5 per cent have tested positive for coronavirus. Only 16 of the 204 people who became infected had been vaccinated. Those who got "breakthrough" infections after one or two doses of vaccine had 40 per cent less virus in their bodies and were 58 per cent less likely to have a fever. They spent two fewer days in bed than unvaccinated Covid-19 patients.

"Findings from the extended timeframe of this study add to accumulating evidence that mRNA COVID-19 vaccines are effective and should prevent most infections — but that fully vaccinated people who still get COVID-19 are likely to have milder, shorter illness and appear to be less likely to spread the virus to others. These benefits are another important reason to get vaccinated," the statement said.

ICMR study

A study by the Indian Council of Medical Research (ICMR) in Odisha among those fully vaccinated has found that around 10 per cent of those reporting a breakthrough infection that bypass vaccine protection required hospitalisation. The preliminary study conducted during March 1 and June 10, which is yet to be peer-reviewed, found that 9.9% required hospitalisation with no significant difference between Covaxin and Covishield recipients and around 83.2% were symptomatic.

Only one healthcare worker died after being infected during the study period and the median duration of hospitalisation among the reported cases was 11 days with one person still in the hospital. The most common symptoms found was fever, followed by cough and sore throat. Co-morbidities such as diabetes, hypertension, hypothyroidism and asthma were present in about 64 people.

The authors of the study said there were two limitations of the study. The number of documented vaccination breakthrough cases may be significantly a small fraction of all such cases. They also said that the study might not be a complete representation of breakthrough cases.

Fortis study

A study released by Fortis Healthcare on June 17 found that a majority of fully vaccinated healthcare workers developed only mild illness after contracting the coronavirus disease and largely recovered under home care despite a surge in serious infections during the second wave of the pandemic. Only 1 per cent of fully vaccinated healthcare workers, who were infected after getting the shots, needed ICU care or ventilator support, the study said.

The study assessed around 16,000 healthcare workers, who got both doses of vaccine between January and May this year. This included the peak period of the second wave when India was recording 350,000 to 400,000 Covid-19 cases each day and healthcare workers were working round the clock. Only 6 per cent of staff got infected after receiving both doses of the Covid-19 vaccine, according to the Fortis study.

Amongst those who got infected after getting fully vaccinated, 92 per cent were mildly infected cases, 7 per cent developed moderate illness requiring oxygen support and only 1 per cent developed severe illness requiring ICU care or ventilation.

The study emphasised that the vaccines available in India against Covid-19 are effective and do offer protection against the SARS-CoV-2 virus.