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Moderna COVID-19 Vaccine Offers At Least 6 Months of Protection

Older adult getting a bandaid post-vaccination.

Jasmin Merdan / Getty Images

Key Takeaways

  • A research study, published by the New England Journal of Medicine, found that the Moderna vaccine offered at least six months of protection against COVID-19. 
  • As people age, their bodies become less responsive to vaccines so COVID-19 boosters may be needed in the future. 
  • Because of the spread of variants, experts advise that the general public remain vigilant and continue practicing COVID-19 safety precautions until further research is conducted.

If you've received two doses of the Moderna vaccine, scientists are getting closer to pinpointing exactly how long you'll be protected. New research suggests your vaccine-induced antibodies will protect you from COVID-19 for at least six months.

Lead study author Nicole Doria-Rose, PhD, a scientist at the National Institutes of Health, tells Verywell antibodies—which are proteins in the blood that fight viruses—were found in healthy adults up to six months after their second Moderna dose. “So seeing that the antibodies are around for six months means that it will be at least six months before you need to get a booster,” Doria-Rose says.

To measure antibodies, study author Mehul Suthar, PhD, assistant professor in the department of pediatrics at Emory University, tells Verywell the team used a method called neutralization assays, an investigative procedure that takes part of the virus that contains spike proteins and mixes it with the patient's blood to see the capacity of a patient’s blood sample to block the virus. 

Antibody presence is particularly important when looking at vaccine efficacy, Suthar says. “We ask what’s the capacity of that patient’s blood sample at different dilutions to block the virus from infecting a cell,” Suthar says. “The antibodies bind to the appropriate regions in the virus to prevent it from actually infecting a cell.” 

Because the presence of antibodies slowly decreases over time, Doria-Rose and Suthar looked at how antibodies would hold up. “They don’t stay at a constant level,” Doria-Rose says. Six months after their second dose, antibodies remained high in all age groups.

What This Means For You

For people who have received the Moderna vaccine, roughly two weeks after the second dose, the vaccine was found to be 94% effective at protecting against COVID-19. So if you've been fully vaccinated with the Moderna two-dose regimen your immunity may last up to six months. You may need to receive a booster shot in the future, but that remains to be determined.

Older Populations Saw a Decrease in Antibodies

The small study looked at 33 participants from the initial Moderna vaccine clinical trials. Researchers examined three different age groups:

  • 18 to 55 years
  • 56 to 70 years
  • 71 years or older 

They discovered that the prevalence of antibodies did decrease in older participants. For example, levels of antibodies—also known as titers— averaged around 92,000 for vaccinated people aged between 18 and 55 six months after their second dose. However, in people 56 to 70, titers dropped to about 62,000, and in people 71 and older they averaged about 49,000.

A potential explanation for decreased antibodies in older age groups involves the strength of the immune system, according to Doria-Rose. "Older people have immune systems that aren’t as strong as younger people’s immune systems,” Doria-Rose says. Research shows that older people have reduced vaccination longevity and levels of antibodies post-vaccination.

Because older folks become less responsive to vaccines with age, Doria-Rose says booster shots may be needed in the future. 

How Variants Factor In

The tricky part about navigating COVID-19 is vaccine development against variants of the virus, Suthar says. Since the onset of vaccine rollout, the virus has developed mutations within the spike protein that can make the virus more contagious.

Initially, the vaccines were designed to protect people against the first COVID-19 strain. Now, new mutations pose a challenge to vaccine development. “There are other troubling variants out there, the Brazilian one, the South African variant, that increase the ability of the virus to not only transmit better but also possibly escape some of the antibody responses,” Suthar says.

When new variants are discovered, this poses a challenge to researchers like Suthar and Doria-Rose. “The more times the virus is able to do this in nature [mutate], the better the virus would be able to infect, replicate, spread, mutate,” Suthar says. “One of the byproducts is it can now develop ways to be able to evade antibody response.” 

Despite the fact that current vaccines offer antibody responses against the U.K. B117 variant, Suthar stresses that the public should still observe safety precautions. “I think we still need to be vigilant and wear masks using the appropriate precautions of social distancing,” Suthar explains. “We just hope that the vaccines that have been designed still maintain that level of protection against these variants.” 

Booster Shots

Doria-Rose says the research of antibody perseverance will continue to explore the long-term antibody response for Moderna’s COVID-19 vaccine, especially the antibody response after one year. “We’re going to be doing the one-year samples soon," Doria-Rose says. "Then we’re actually testing whether a booster shot will do—that’s being tested in the next couple of months."

Whether you may have to get a booster shot in the future to bolster your immunity to the virus remains to be seen. But despite how long protection lasts, the advice remains the same: "When it is your turn to get vaccinated, when you have the opportunity to do so, get vaccinated,” Doria-Rose says. 

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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  2. Lord JM. The effect of aging of the immune system on vaccination responses. Hum Vaccin Immunother. 2013;9(6):1364-1367. doi:10.4161/hv.24696