Full vaccination plus breakthrough infection equals 'super immunity'

USA Today

A study by Oregon researchers finds that people fully vaccinated against COVID-19 who have a breakthrough infection end up with what the authors call "super immunity."

They caution the vaccinated should not seek COVID-19 infection, but the "hybrid immunity" offers some solace for those who catch one despite having been vaccinated.

"The bottom line of the study is that vaccine provides you with foundational immunity for whatever comes next," said Fikadu Tafesse, a professor of molecular microbiology and immunology in the Oregon Health & Science University School of Medicine in Portland, Oregon.

The study matched 26 vaccinated Oregon Health & Science University staff people who had breakthrough infections with a similar group who were vaccinated but hadn't had COVID-19.

The people who were vaccinated and then got COVID-19 showed a substantial increase in antibody levels, said Tafesse.

"The increases were substantial, up to a 1,000% increase and sometimes up to 2,000%, so it's really high immunity," he said. "It's almost 'super immunity.'"

Multiple other studies have shown that infection with COVID-19 followed by one dose of the vaccine is very protective against re-infection.

“This is one of the first that shows a breakthrough infection following vaccination generates stronger immunity than prior infection or vaccination alone,” said Dr. Monica Gandhi, an infectious disease expert at the University of California, San Francisco.

While possibly equally protective, the reverse order is not recommended. Getting COVID-19 before being vaccinated is dangerous because “we cannot predict who will get very ill with COVID,” Gandhi said.

As the highly contagious omicron variant continues to spread in the United States, the findings will be of interest to many, and "is likely what the future will hold for most vaccinated individuals," Gandi said.

Omicron appears to be able to infect even fully vaccinated people, though they so far appear to come down with mild or even asymptomatic cases of COVID-19.

"What we're saying is, we know life happens. If you happen to be exposed to the virus, you'll have this amazing immune response," Tafesse said. "It mirrors the immunity response we get from the booster."

The finding shows what a good job the immune system does, said Shane Crotty, a professor at the La Jolla Institute for Immunology in California.

Every time the immune system sees the vaccine or the virus, it is learning more and better able to fight it and potential other variants.  “This is what the immune system evolved to do, to make guesses from something it’s been exposed,” he said.

There is some information being spread online claiming that getting vaccinated after having recovered from COVID-19 is dangerous because it could overstimulate the immune system.  "That's completely made up, it's total rubbish," said Crotty. "It was tested in all the vaccine trials. Getting vaccinated after COVID-19 exposure is totally safe."

Getting a booster is still safer than getting COVID-19, said Dr. Gregory Poland, director of the Mayo Clinic's Vaccine Research Group, particularly for those at risk for severe disease, including those over 70, people with diabetes and those with weakened immune systems.

"Best is getting three doses of an mRNA vaccine and never getting infected. Complications, including long COVID and transmission to others, represent a risk even in that scenario," Poland said.

He offered a hierarchy of safety:

Best scenario: Fully vaccinated and boosted, no infection upon exposure

Next best: Fully vaccinated, boosted and asymptomatic or mild disease upon exposure/infection

Next best: Fully vaccinated, boosted, moderate disease and attendant complication risks upon infection

Worse: not fully vaccinated or boosted and risk severe disease/death and its risks upon infection

For those who have had COVID-19 and don't think they need to get vaccinated, Crotty suggested thinking of it another way.  "If you get at least one dose of vaccine, you'll have the best immunity of anyone," he said. "You'll have amazing immunity against omicron and any variant that's been identified."