- Immunity can occur naturally after developing COVID-19, from getting the COVID-19 vaccination, or from a combination of both.
- In June 2022, the CDC reported that BA.4 and BA.5 subvariants of Omicron became the predominant subvariants in the U.S.
- Infections with variants before Omicron or being fully vaccinated appear to be less effective at preventing immunity against BA.4 and BA.5.
- Scientists are learning more and more about the length of immunity after developing COVID-19, getting the vaccine, or both.
Whether you’ve recovered from COVID-19, received the vaccine, or both, understanding immunity and how long it lasts can help give you important insight into how you can interact safely with others during the pandemic.
First, it helps to know what immunity means.
There are a few types of immunity: natural, vaccine-induced, and hybrid.
After a person acquires a virus, the immune system retains a memory of it.
The components of immunity protection include:
- Antibodies are proteins that circulate in the blood and recognize foreign substances like viruses and neutralize them.
- Helper T cells help to recognize pathogens.
- Killer T cells kill pathogens.
- B cells make new antibodies when the body needs them.
People who recover from COVID-19 have been found to have all four of these components. However, specifics about what this means for the immune response and how long immunity lasts are not clear.
Dr. William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center, said it’s not known exactly how long the protection after natural infection will last and how durable that protection will be against a variety of different variants.
“There are some people who have the notion that after you’ve gotten a natural infection, you will be permanently protected against COVID-19 as if this were measles. But the two viruses that cause these infections are very, very different. The coronavirus protection wanes naturally after a period of time,” Schaffner told Healthline.
Because COVID-19 is caused by a coronavirus, which is the type of virus the common cold is also caused by, he said researchers have an understanding of how other coronaviruses behave, which may help understand immunity for COVID-19.
“We all know we can get repeated common colds, and the studies on those viruses indicate that their protection begins to wane after about a year, and of course, we can get new infections down the road,” he said.
Because new variants continue to emerge, it’s difficult to measures just how long natural immunity lasts.
In June 2022, the Centers for Disease Control and Prevention (CDC) reported that BA.4 and BA.5 subvariants of Omicron became the predominant subvariants in the U.S.
Infections with variants before Omicron or being fully vaccinated appear to be less effective at preventing immunity against BA.4 and BA.5.
A study out of Harvard Medical School published in July 2022, found that previous infection from COVID or having been vaccinated doesn’t provide as much protection against the BA.4 and BA.5 variants as either did for the original coronavirus strain.
However, another study in Qatar that has not been peer-reviewed found that immunity developed after recovering from Omicron was 80% effective against reinfection with the BA.4 or BA.5 subvariants.
Researchers from the Harvard study note that vaccination should still provide protection against severe illness even with infection from BA.4 or BA.5.
Additionally, a study from July 2022 looked at vaccinated people and their antibody titers, which measures the amount of antibodies in their blood. Researchers reported that the BA.2.12.1, BA.4, and BA.5 subvariants substantially escape neutralizing antibodies induced by both vaccination and infection.
In an older South African study from December 2021, researchers determined that the risk of reinfection from Omicron is 3 times higher than it is for previous strains of the virus.
The researchers analyzed 2,796,982 people who had positive test results at least 90 days before November 27, 2021. People who had sequential positive tests at least 90 days apart were considered to have suspected reinfections.
Based on their analysis, the researchers found:
- No evidence of increased reinfection risk associated with Beta or Delta variants compared to the original strain.
- The Omicron variant is associated with a substantial ability to evade immunity from prior infection.
The CDC reported that
For instance, in clinical trials, the Moderna vaccine was about 94% effective at preventing COVID-19 and the Pfizer-BioNTech vaccine was 95% effective.
Real-world data also show that Pfizer and Moderna vaccines are effective at reducing the risk of COVID-19, including severe illness, by
The Johnson & Johnson vaccine was
Time is needed to track how well Novavax does in the real world. However, results from a Phase 3 clinical trial that included nearly 30,000 adults in the United States and Mexico found that it demonstrated 90.4% efficacy in preventing symptomatic COVID-19 disease, according to the
While the Pfizer, Moderna and Novavax vaccines require two shots a few weeks apart to get full protection, Johnson & Johnson only requires one shot.
Once you have full vaccine protection, your body is left with a supply of T cells as well as B cells that will remember how to fight the virus in the future, just like they do with natural immunity.
However, it usually takes a few weeks for the body to produce T cells and B cells after vaccination. During this time, it’s possible to acquire the virus that causes COVID-19 until your body can provide protection.
In a Q&A with the World Health Organization (WHO),
As of May 19 2022, the
This allows for a single booster dose of the Pfizer and Moderna COVID-19 vaccines that may be administered at least 5 months after completion of the primary series for most people or at least 3 months after the final dose in the primary series for those who are moderately or severely immunocompromised. Additionally, the CDC recommends a second booster of either Pfizer-BioNTech or Moderna COVID-19 vaccine at least 4 months after the 1st booster for people 50 years and up or those who are 12 and older who are moderately or severely immunocompromised.
Adults up to 49 years old who received the Johnson & Johnson vaccine for both their primary dose and booster can get a second booster of either Pfizer-BioNTech or Moderna COVID-19 vaccine at least 4 months after their 1st booster. However, the second booster is not required to be considered up to date for this age group who got the Johnson & Johnson vaccine for both their primary dose and first booster.
While the CDC states that COVID-19 vaccination remains effective in preventing severe disease, it points to
Schaffner added that while the vaccines are explicitly designed to create a large immune response, they are not 100% effective, and therefore the need for a booster shot may become standard like it is annually for the flu, especially to protect against
Additionally, the FDA authorized that each of the available COVID-19 vaccine boosters can be mixed and matched in eligible people following completion of primary vaccination.
The FDA took various data into consideration when it authorized the use of boosters.
On June 17, 2022, the FDA expanded the emergency-use authorization (EUA) for the Moderna and Pfizer-BioNTech COVID-19 vaccines to children down to 6 months old.
“Children are less apt to get serious disease, but they can get serious disease,” said Schaffner.
According to Unicef, over 17,200 people under the age of 20 have died from COVID, of which 53% were children aged 10 to 19 and 47% were aged 0 to 9.
“[For] those families, it’s 100%,” said Schaffner.
Getting children vaccinated is crucial as more variants like Omicron develop, and existing ones like Delta still circulate, he said.
“We all know about Omicron and we got very excited about it, but… [Delta] is much more contagious than the original strain, and it’s clearly moving into the pediatric population now, so its behavior was different from the original strain, and that gives even more reason to vaccinate children,” he said.
To keep kids fully protected, the CDC recommends the following in terms of boosters for those who received the Pfizer primary series:
5–11 years old
CDC recommends a booster of Pfizer vaccine for:
- Most children, at least 5 months after the final dose in the primary series
- Children who are moderately or severely immunocompromised, at least 3 months after the final dose in the primary series
- Not recommended for this age group.
12–17 years old
CDC recommends a booster of Pfizer vaccine for:
- Most children and teens, at least 5 months after the final dose in the primary series
- Children and teens who are moderately or severely immunocompromised, at least 3 months after the final dose in the primary series
- CDC recommends a 2nd booster of Pfizer vaccine at least 4 months after the 1st booster for children and teens who are moderately or severely immunocompromised
One study found that hybrid immunity can provide protection for more than a year.
“We know that after you’ve had natural infection, and then get vaccinated, you get a terrific boost in your antibody levels. And very high antibody levels traditionally have been associated with longer duration of protection. And in the laboratory, it looks as [if] those antibodies also provide a better protection against variants,” said Schaffner.
According to current CDC data, 78.7% of people have had at least one dose of the vaccine
and as of April 2022,
surge of BA.4 and BA.5 may mean this number is higher.