Covid antibodies found in 95% of study participants despite half believing they were never infected

'Only two people out of the 445 had not been vaccinated, so the fact we are all vaccinated basically means we might have been exposed but the vaccine has helped prevent this from developing into a full-flight infection.'

A new study on Covid-19 antibodies found 95% of a sample group of participants showed signs of having the virus despite more than half believing they had never been infected.

The preliminary findings, part of the University College Cork UniCoV project, indicate vaccines are protecting people from severe illness, principal investigator Dr John MacSharry said.

The research focused on Covid-19 antibodies in the blood, which indicates past infection of the virus.

“We asked people do you think you have been exposed to Sars-CoV-2 and have you had symptoms,” he said.

“It was 46% that believed they had been exposed and 54% believed they had not been exposed. Then when we did the antibody tests, only 5% of all the 445 [in the group] were actually not exposed.” 

He said further tests were being done, with final results expected to be published shortly.

“Only two people out of the 445 had not been vaccinated, so the fact we are all vaccinated basically means we might have been exposed but the vaccine has helped prevent this from developing into a full-flight infection,” he said.

“We were still exposed and our body developed antibodies against it.” 

Some people returned for a second test after infection during the June wave, and he said these rapid antibody tests showed clearly increased levels.

“One of the key things as well is that most people thought they hadn’t been exposed to Covid, and they had been,” he said.

Restrictions ended really in March, everyone is going back to normal but the virus is still going to replicate in humans as long as there are humans present. We are probably going to get a surge in October again.” 

Dr MacSharry, lecturer in molecular microbiology at UCC, is hopeful companies developing these tests will bring them to the commercial market.

“These point-of-care tests could be very useful,” he said. “You could say ‘look, your antibody levels look a little low, you need to go and get a booster’. “ 

They could be used in nursing homes, he suggested, and with other vulnerable people to ensure they are getting boosters in time to prevent infection.

“If you were low [in antibodies], you could get it done in a pharmacy or a drop-in clinic, or you could do it yourself,” he said.

This could help people avoid Covid infections by keeping their booster schedule linked to protection levels, Dr MacSharry said.

“The key message really is to show vaccination does work,” he said.

“But you still can get infected if you are vaccinated and your antibody levels are dropping off. It’s quite normal for coronavirus, which is the family of the virus SAR-CoV-2, that you have roughly a six-month immunity, up to six months.” 

The study used different types of antibody tests to differentiate between antibodies arising from vaccination or from infection. 

The team also includes Professor Mary Horgan, infectious diseases consultant at Cork University Hospital, and head of student Hhealth Dr Michael Byrne.

It is part of the UniCoV projects running across four Irish universities.

These findings follow HPSC seroprevalence tests (levels of Covid-19 in blood) indicating 69% of the population had the virus, and 87% of people aged 20 to 29.