Hybrid immunity, new breakthrough infections bring pandemic closer to end: US study

Amid concerns over Omicron, a new study has revealed that breakthrough infections are bringing the pandemic closer to an end.

Oregon Health & Science University (OHSU) research revealed more than one path toward robust immunity from COVID-19.

 “I would expect at this point many vaccinated people are going to wind up with breakthrough infections – and hence a form of hybrid immunity,” said senior co-author Bill Messer, assistant professor of molecular microbiology and immunology and medicine (infectious diseases) in the OHSU School of Medicine

OHSU scientists said with the spread of the highly contagious Omicron variant, many unvaccinated people who were previously infected are likely to confront the virus again.

 “I can guarantee that such immunity will be variable, with some people getting equivalent immunity to vaccination, but most will not,” he said. “And there is no way, short of laboratory testing, to know who gets what immunity. Vaccination makes it much more likely to be assured of a good immune response,” senior co-author Marcel 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. 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,” he said.

The study noted that breakthrough infections following vaccination or natural infection followed by vaccination provide equal levels of enhanced immune protection against COVID 19.

The new study found that it doesn’t matter whether someone gets a breakthrough infection or gets vaccinated after a natural infection. In both cases, the immune response measured in blood serum revealed antibodies that were equally more abundant and more potent – at least 10 times more potent – than immunity generated by vaccination alone.

The study was done before the emergence of the Omicron variant, but researchers expect the hybrid immune responses would be similar to the new highly transmissible variant.

“The likelihood of getting breakthrough infections is high because there are so many viruses 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,” Tafesse said. 

Researchers recruited a total of 104 people, all OHSU employees who were vaccinated by the Pfizer vaccine, and then carefully divided them into three groups: 42 who were vaccinated with no infection, 31 who were vaccinated after an infection, and 31 who had breakthrough infections following vaccination. Controlling for age, sex, and time from vaccination and infection, the researchers drew blood samples from each participant and exposed the samples to three variants of the live SARS-CoV-2 virus in a Biosafety Level 3 lab on OHSU’s Marquam Hill campus.

They found both of the groups with “hybrid immunity” generated greater levels of immunity compared with the group that was vaccinated with no infection.