Follow us for updates
© 2022
Read the Story →

Natural Immunity Stronger Than Vaccines During Delta Wave: U.S. Study

Researchers however warn against infection as strategy.
by Agence France Presse
Jan 21, 2022
Photo/s: Shutterstock

WASHINGTON -- During America's last surge of the coronavirus driven by the delta variant, people who were unvaccinated but survived COVID-19 were better protected than those who were vaccinated and not previously infected, a new study said Wednesday.

The finding is the latest to weigh in on a debate on the relative strengths of natural versus vaccine-acquired immunity against SARS-CoV-2, but comes this time with the imprimatur of the U.S. Centers for Disease Control and Prevention (CDC).

The authors of the paper warned, however, against depending on infection as a strategy, given the higher risks to unvaccinated persons who weren't previously infected of hospitalization, long term impacts, and death, compared to vaccinated people.

Indeed, by Nov. 30, 2021, some 131,000 residents of California and New York had died from COVID-19, the two states the paper, which used statistical modeling, was based on.

"Viruses are constantly changing, including the virus that causes COVID-19," the CDC said in a statement. 

Continue reading below ↓

"The level of protection offered by vaccination and surviving a previous infection changed during the study period. Vaccination remains the safest strategy for protecting against COVID-19," it added.

The analysis was also carried out before the emergence of the omicron variant, for which both vaccine and infection-derived immunity appear diminished, and before boosters were made widely available.

It used case data from 1.1 million people who tested positive in New York and California between May 30 to Nov. 30, 2021, and used that to model inferences about the wider population.

Prior to Delta becoming dominant, vaccination conferred greater immunity than infection. But the relationship shifted when the variant became predominant in late June and July.


That Herd Immunity Strategy vs COVID-19? Unethical Says WHO

Omicron Might Evade Antibodies, But That Doesn't Mean You Don't Have Immunity

Can COVID-19 Strike Twice? Scientists Say Yes, And It Casts Doubts on Immunity

Continue reading below ↓
Recommended Videos

Selection bias?

By the week of Oct. 3, vaccinated people who did not have prior COVID-19 were three to four times (in California and New York, respectively) more likely to be infected than unvaccinated people with prior COVID-19.

In the weeks of Oct. 13 to Nov. 14, vaccinated people who did not have prior COVID-19 in California, were around three times more likely to be hospitalized than unvaccinated people with prior COVID-19.

Protection was highest among those who had both vaccination and prior COVID-19.

The study could however be impacted by an effect known as "selection bias," since it excluded people who died, who were overwhelmingly unvaccinated.

Other research, including a notable paper from Israel in August, have also found that natural immunity was more potent than vaccines during the delta surge. 

But the U.S. CDC had previously taken the opposite position, based on pre-delta data.

"Further studies are needed to establish duration of protection from previous infection by variant type, severity, and symptomatology, including for the omicron variant," the paper concluded.

Continue reading below ↓

Reportr is now on Quento. Download the app or visit the Quento website for more articles and videos from Reportr and your favorite websites.

Latest Headlines
Read Next
Recent News
With the reopening of several local destinations, this app has never been more timely.
The focus should be on the poor, incoming senator said.
GCash isn't just about paying bills and transferring funds.
You'll need a bigger wallet, incoming BSP gov says.
The news. So what? Subscribe to the newsletter that explains what the news means for you.
The email address you entered is invalid.
Thank you for signing up to On Three, reportr's weekly newsletter delivered to your mailbox three times a week. Only the latest, most useful and most insightful reads.
By signing up to newsletter, you agree to our Terms of Service and Privacy Policy.