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Researchers say that prior infection and vaccination both offer strong protection against serious illness from COVID-19. Getty Images
  • When we’re vaccinated or have had a previous infection with a virus, our bodies are able to mount an antibody response when we’re exposed to the pathogen again.
  • A new study reports that prior infection and vaccination both offer strong protection against the Delta strain of the coronavirus that causes COVID-19.
  • Experts say that the research shows the importance of getting vaccinated whether you’ve had a previous case of COVID-19 or not.

Does a previous case of COVID-19 make you immune from future infections?

Does it mean that there isn’t a need to get vaccinated?

With all the new information that comes out daily on COVID-19, it may be difficult to know what to do. But some new research may help shed some light.

In a new study, researchers reported that vaccination plus infection provides strong protection against the Delta strain of the coronavirus.

The researchers presented the following additional findings:

  • Those who recovered from COVID-19 were less likely to get an infection with the Delta strain than those who were vaccinated. Case and hospitalization rates were also lower among those who had recovered from COVID-19 compared to those who were vaccinated.
  • Both vaccination and a prior infection offered substantial protection against serious illness and hospitalization.
  • People who weren’t vaccinated and hadn’t had a previous infection were far more likely to develop COVID-19 and be hospitalized than those who were previously infected or vaccinated.

This study covered the period from May 30, 2021 to November 20, 2021, so it focused on the Delta strain. The data was collected before the emergence of the Omicron strain and the arrival of booster shots.

“The most direct conclusion is that for the Delta, and possibly the Omicron, natural immunity confers very strong protection,” said Dr. Iahn Gonsenhauser, the chief quality and patient safety officer and an assistant clinical professor at The Ohio State University’s Wexner Medical Center.

The fact that people who had already had COVID-19 were less likely to contract the Delta strain of the coronavirus may lead some to think they don’t need to get vaccinated.

“Not true,” says Dr. Nathaniel Soper, an Instructor of internal medicine at the University of Michigan. “For people who have not previously had COVID-19 and are unvaccinated, my advice continues to be that vaccines are incredibly safe and highly effective at preventing severe infection and hospitalization.”

Soper noted that contracting the virus still has risks, even if you’ve had a previous bout of the disease.

“It is dangerous to avoid vaccination and try to get COVID-19 to hope for protection,” Soper told Healthline. “For example, the possibility of long COVID symptoms, straining the healthcare system, requiring time off work, and the risks of passing the infection to others who may be more prone to severe disease.”

Gonsenhauser noted that there’s a decrease in vaccine effectiveness as time moves on.

“As Omicron continues to replace all other variants, we are experiencing a lower severity version of the virus,” Gonsenhauser told Healthline.

“It makes perfect sense that vaccine-mediated and natural immunity differences are becoming less significant. Remember, the vaccine was always about lowering the severity of infection, not avoiding disease altogether.”

A new study from Japan explains how our bodies respond to vaccines and infections.

Researchers explained that when you’re first vaccinated or contract the coronavirus, it leads to a blast of antibody production.

These antibodies work to eliminate a potential infection within a short time. In the case of vaccinations, experts have suggested booster shots after 6 months because of waning immunity.

In the event you get an infection months after the original antibodies, your body responds by forming a new batch of antibodies.

These include long-lived cells that carry a memory of the pathogen and offer better protection against future infections.

However, because the coronavirus is a new virus, scientists are unsure how long this protection lasts.

Experts say that the main message here is: Vaccines work.

They help prevent severe illness and lower the chance of being hospitalized if you develop COVID-19.

“For those who are healthy and not considered at high risk of serious illness, I would [still] recommend the vaccine,” said Soper.

“Even those at low risk for severe infection, any potential risks of vaccination are still far outweighed by the risks of infection,” he added.

“We regularly see young, healthy people (20s and 30s) with severe infections. They may end up in intensive care units, and symptoms related to even mild infections can persist for a long time and be very debilitating.”