Getting infected after getting Covid triggers ‘super-immunity’

Fully-vaccinated people who catch Covid end up with ‘super immunity’, scientists have claimed.

Oregon Health and Science University experts say the same is also true for people who get infected before getting two jabs. 

Academics took blood samples from more than 100 fully-vaccinated volunteers and exposed them against three different strains of coronavirus.  

Volunteers with ‘hybrid’ immunity produced an ‘amazingly high’ antibody response, tests showed.

Their antibodies were 10 times more potent than proteins made by participants who managed to dodge Covid completely.

Despite the study being carried out before the emergence of Omicron, the authors believe the findings will hold up against the highly-transmissible variant.

And the high levels of protection among those with hybrid immunity could see the virus become a ‘mostly mild’ infection and bring about the end of the pandemic, the researchers said.

Author Dr Fikadu Tafesse said: ‘It makes no difference whether you get infected-and-then-vaccinated, or if you get vaccinated-and-then-a-breakthrough infection.

‘In either case, you will get a really, really robust immune response – amazingly high.’

He added: ‘The likelihood of getting breakthrough infections is high because there is so much virus around us right now. 

‘But we position ourselves better by getting vaccinated. And if the virus comes, we’ll get a milder case and end up with this super immunity.’

Fully-vaccinated people who caught Covid (shown in graphic, left) before or after they were jabbed end up with ‘super immunity’, scientists at Oregon Health and Science University claimed. Pictured right: vaccine stock image

The scientists took blood samples from 104 university employees who were double-jabbed with Pfizer.

Volunteers were divided into three groups based on their previous infection status. Forty-two participants had never tested positive. 

All of the others had either caught the coronavirus before being vaccinated, or were infected after getting their two jabs.

The experts exposed their blood to three Covid variants: Alpha, Beta and Delta.

The results — which mirror previous findings by the same team — were published in Science Immunology.

Immunologists say antibody levels correlate quite well to protection against Covid infection.

But they are not a fool-proof way of measuring immunity because other parts of the immune system also defend against the virus.

Antibodies work to stop an infection taking hold by attacking the virus, preventing it from binding to and infecting cells. 

But if the virus breaches that defence, T cells can identify and kill off infected cells to stop them spreading further. These white blood cells are thought to provide longer-lasting protection against the virus compared to antibodies which wane within months. 

The study was completed before Omicron was first detected in November — but the scientists expect that the immune response to the new variant will be similar.

The scientists also didn’t compare antibody levels between hybrid immunity and those who are triple-jabbed.

But the findings could mean that every new breakthrough infection — when people test positive despite being vaccinated — ‘potentially brings the pandemic closer to the end’, the team said. 

Fellow researcher Dr Bill Messer said: ‘I would expect at this point many vaccinated people are going to wind up with breakthrough infections – and hence a form of hybrid immunity.’  

Dr Marcel Curlin, study author and infectious disease expert, said: ‘These results together with our previous work point to a time when SARS-CoV-2 may become a mostly mild endemic infection like a seasonal respiratory tract infection instead of a worldwide pandemic.’

However, they warned that unvaccinated people are likely to catch Covid multiple times and their immune response is ‘much more variable’.

Some will get ‘equivalent immunity to vaccination, but most will not’ and there is no way to know how much immunity someone has without laboratory tests, the team said.

Dr Curlin said: ‘Immunity from natural infection alone is variable. Some people produce a strong response and others do not.

‘But vaccination combined with immunity from infection almost always provides very strong responses.’