Study: Protection from prior COVID infection almost as good as vaccines

A recent meta-analysis in the Lancet compared protection conferred upon individuals by prior infection from COVID-19 and vaccination against the virus and found protection from a prior COVID infection to be on par with the shot.

But one expert argued that this interpretation misses the nuances in the meta-analysis, which looked at 65 studies from 19 countries published up until Sept. 30, 2022, and therefore could not fully take into account how prior infection fared against the omicron variant and its growing list of subvariants.

In addition, researchers equated a two-dose mRNA vaccine to prior infection and didn’t consider a booster, said Kevin Kavanagh, president and founder of patient advocacy group Health Watch USA, in an interview with Fierce Healthcare.

“I feel the meaning of the results of the study has been largely misinterpreted,” Kavanagh said. “Infection may give similar or greater immunity than a two-dose vaccine, but both are inadequate at this point,” he adds.

Meanwhile, healthcare industry players tout the need for vaccination. The American Academy of Family Physicians, for instance, which represents about 127,000 physicians and medical students nationwide, has continuously emphasized the effectiveness of COVID-19 vaccines for children as well as adults.

A spokesperson for the Blue Cross Blue Shield Association (BCBSA) told Fierce Healthcare by email that the organization “is supportive of the COVID-19 vaccine as a method of protection against the coronavirus and to help prevent the spread of COVID-19. BCBSA is committed to reducing barriers to COVID-19 vaccines and supports the equitable access to vaccines across the country as well as educating Americans on the safety and efficacy of vaccines.”

Employers are also looking at the shifting landscape regarding vaccination requirements.

Randa Deaton, is vice president of purchaser engagement for the Purchaser Business Group on Health, an organization representing about 40 large public and private employers that spends about $350 a year on healthcare for more than 21 million beneficiaries. Deaton tells Fierce Healthcare in an email that “at this time, some employers are thinking about eliminating vaccination requirements. Given that, it seems unlikely that large companies would choose to track infection rates, which would be practically very difficult to do even if the interest was there.”

In the meta-analysis, researchers with the Institute for Health Metrics and Evaluation (IHME) at the University of Washington found that “only a small number of studies were identified that evaluated protection from past infection against omicron sublineages such as BA.2 and BA.4 and BA.5.”

The study also found the risk of hospitalization because of COVID-19 for adults who’d been previously infected to be 89% to 90% lower for at least 10 months than adults who’d not been previously infected or vaccinated.

Protection against wild-type, alpha and delta variants had fallen to 78.6% after 10 months for those who’d been previously infected, while protection against omicron fell to 36.1%. Nonetheless, protection against hospitalization and death for the wild-type, alpha and delta variants was 90.2% after 10 months and 88.9% for omicron.

Those results don't impress Kavanagh, he said.

“If at the beginning of the pandemic, back in 2020, we announced that a vaccine would give protection for about 10 months, that it was only 36.1% effective in preventing infections with the tested BA.1 variant, and it would be expected to be less effective with the current circulating variants, few would view this as good news,” he said.

Kate Grusich, a spokesperson for the Centers for Disease Control and Prevention (CDC), told Fierce Healthcare in an email that the agency “recommends COVID-19 vaccination for everyone ages 6 months and older, regardless of a history of symptomatic or asymptomatic SARS-CoV-2 infection. This includes people with prolonged post-COVID-19 symptoms, and applies to our recommendations for both primary series and booster doses.”

Individuals who’ve recently been infected by COVID-19 might want to consider delaying the primary vaccine dose or booster shot by three months from the onset of symptoms or if they’ve tested positive for the virus but are asymptomatic, she said.

“Individual factors such as risk of COVID-19 severe disease, COVID-19 community level, or characteristics of the predominant SARS-CoV-2 strain should be taken into account when determining whether to delay getting a COVID-19 vaccination after infection,” Grusich said.

The BCBSA spokesperson added that “even if patients have already been infected, the CDC recommends COVID-19 vaccination as it provides added protection against COVID-19. Blue Cross and Blue Shield plans will continue to cover vaccinations as recommended by the CDC, which updates its recommendations based on evolving research and progression of the virus.”

IHME researchers in the Lancet study said they believe their findings have public policy implications. They suggested providers should track prior infection rates and the type of variant individuals might have been infected by. In addition, vaccine mandates for workers should also include prior infection status.

“Countries have taken different approaches to this; for example, immunity from past infection was considered as part of eligibility for the EU COVID certificate but not in countries such as the U.S.A. or Australia,” the meta-analysis said.

The authors also argued that protection because of past infection should be taken into account when considering when individuals should get a vaccine or booster. That prior infection doesn’t seem to block reinfection when the omicron variants are involved should spur timely epidemiological studies when new variants crop up, they argue.

They added, though, that “it is important to note that the ability to assess protection conferred by infection, by comparing individuals unvaccinated and previously infected to those who are unvaccinated and COVID-19 naive, is increasingly challenging given the small number of people who are unvaccinated and COVID-19 naive remaining in many populations.”

Kavanagh said “preventing hospitalizations and deaths is important, but we now know that long COVID is also a grave concern, one which can occur in mild disease. Data from the CDC Household Pulse Survey indicates it is even more common in young and middle-aged adults than those above the age of 60. The results of the article underscore the necessity for both vaccinated and previously infected to receive a bivalent booster to optimize one’s immunity.”