CDC: Previous COVID-19 infection prevents Delta

key takeaways

  • Previous infection with COVID-19 provides some protection against the Delta variant.
  • Vaccination and a history of infection provide the highest defense against Delta.
  • A COVID-19 booster could provide some immunity against Omicron and potential new variants, health experts say.

A new study from the Centers for Disease Control and Prevention (CDC) shows that people who have been previously infected with COVID-19 (both unvaccinated and vaccinated) are more protective of the Delta variant than those who have been vaccinated only— — This suggests that natural immunity is more effective against that particular variant.

Additionally, the researchers found that people who were both vaccinated and who survived COVID-19 infection had the highest levels of protection against Delta during last year’s surge. Protection was lowest in people who had never been infected or vaccinated.

“The people with the strongest immunity are the people with what’s called a ‘mixed immunity,’ who’s getting a vaccine and then getting infected,” California epidemiologist Erica Pan, MD, told VigorTip. “Every time you’re exposed to a vaccine or infected it can boost your immunity.”

Throughout the study period (May 2021-November 2021), people who were vaccinated and previously infected gained immunity and had a lower rate of hospitalization compared with the unvaccinated group.

“These results suggest that vaccination protects against COVID-19 and related hospitalizations, while surviving previous infection protects against reinfection,” the study’s authors said in a press release.

Natural immunity offers some protection

The researchers analyzed data on about 1.1 million cases in California and New York between the end of May 2021 and November 2021. They studied and analyzed the risk of COVID-19 and hospitalization in four groups of people:

  • vaccinated against a previous infection
  • Not vaccinated
  • Not vaccinated against previous infection
  • Unvaccinated and uninfected

In the study’s preliminary findings, those who had been infected had a higher incidence than those who had been vaccinated and had no history of previous infection. But a few months later, those initial findings changed as the Delta variant became more and more dominant in the United States. According to the study, once Delta became popular, those who survived previous infections had lower rates than those vaccinated alone.

“Before the Delta variant, COVID-19 vaccination was better at preventing subsequent infection than prior infection,” Dr. Benjamin Silk, CDC’s surveillance and analysis lead for Epi-Task Force, said on a conference call with the media “However, looking back at the summer and fall of 2021, when Delta dominated the country, surviving a previous infection now provides greater protection against subsequent infection than vaccination.”

Health experts have emphasized that vaccination remains the safest strategy against COVID-19, although prior infection provides some degree of protection and immunity.

“In our data from California and New York, people who are definitely infected do have some protection and are less likely to be hospitalized or die compared to people who have never been infected or have never been vaccinated, but vaccines still is the safest way to protect yourself,” Pan said.

This isn’t the first time researchers have found that innate immunity can provide protection alongside a vaccine. Several studies throughout 2021 reflected these results.

When should you shoot?

The CDC recommends that you get the injection as soon as you recover from the disease, unless you have been treated with monoclonal antibodies. If you have had antibody therapy, you should wait 90 days. Some studies show that antibody levels reach higher counts if you wait 90 days after infection to get vaccinated. The World Health Organization (WHO) says people can consider delaying vaccination for six months after infection. But they add that you should seek advice from your healthcare provider.

The researchers noted that the results of the CDC study did not apply to the Omicron variant of the virus, which accounts for 95 percent of U.S. cases, and did not account for the possible effects of booster doses.

Does this mean it’s better to get COVID-19 naturally?

According to experts like Pan, knowingly contracting COVID-19 is not a better option. Because COVID-19 is an infection itself, when someone becomes infected, it can have serious consequences, including hospitalization and death, she said.

Research from the CDC supports this, noting that there are significant risks in acquiring immunity through natural infection. Specifically, initial infection in unvaccinated people increases their risk of serious illness, hospitalization, long-term effects, and death.

Choosing natural immunity without any protection, such as a vaccine, puts someone at risk of serious illness, Robert G. Lahita, MD, director of the Institute for Autoimmunity and Rheumatology at Saint Joseph Healthcare, told VigorTip.

“If you’ve got COVID and you haven’t been vaccinated, you have no way of knowing if you’re going to get critically ill,” Lahita said. The worst variant we’ve seen on average. On top of that, you are taking a huge risk by not being vaccinated and relying on your natural immunity. ”

Pan added that being infected with COVID-19 can cause long-term effects and symptoms.

“We are learning more and more about long-term COVID and how many people experience long-term symptoms,” Pan said. Systemic issues – like people can’t think right. That’s why vaccination is the best way to protect people.”

How long does natural immunity last?

According to Pan, the duration of immunity depends on the individual and other factors, including what variant they are infected with, how sick the individual was during previous infections, and how old they are.

“How we acquire immunity and how long it lasts are still well-studied, but we don’t yet have a clear and direct answer,” Pan said.

Other experts back this up and say natural immunity can last up to three months or more. Some studies have found that immunity can even last 5 to 12 months. But it depends on the individual.

“We don’t know how long or how long natural immunity will last, because everyone is different,” Rashita said. “One person might get COVID and be immune to the variant for three months, while another person might be Immunization for six months or a year. An antibody test can tell you if you have neutralizing antibodies, and it lasts for a while, but there is absolutely no way to determine how long everyone’s natural immunity lasts.”

what does this mean to you

Vaccination remains the safest measure against the virus and potential new variants. You can find appointments near you here.

What about Omicron and new variants?

The CDC said the data did not apply to the surge in current caused by the Omicron variant, which behaves differently than Delta. Also, the study was conducted before most people received a booster dose.

Despite these factors, the researchers say that as new variants emerge, vaccination remains the safest strategy to prevent COVID-19 infection, severe illness, hospitalization and death. Additionally, primary vaccinations and booster shots are recommended for all eligible individuals.

“Even with a highly contagious variant of Omicron, access to the booster provides a lot of additional protection against infection, hospitalization and death,” Pan said. “In fact, what we’re getting from these data remains that getting the vaccine is the safest way to get protection against COVID-19, and even if you’re already infected, the vaccine still provides additional protection.”

The information in this article is current as of the date listed, which means that you may have updated information as you read this article. For the latest updates on COVID-19, visit our Coronavirus news page.