COVID-19 Vaccine Protection Wanes After 6 Months, Especially for J&J

Tray of COVID vaccines.

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Key Takeaways

  • A new study compares the decline in effectiveness against infection of the three COVID-19 vaccine brands available in the U.S..
  • The vaccines declined in effectiveness significantly after six months.
  • If you're eligible to get your booster shot, you should schedule an appointment as soon as possible.

Numerous studies have already demonstrated that COVID-19 vaccine effectiveness wanes over time. However, a new study is the first to compare this decrease in protection across all three vaccine brands available in the U.S.

The November study, published in Science, examined COVID-19 infection and deaths by vaccination status of more than 780,000 U.S. Veterans. Researchers from the Public Health Institute, the Veterans Affairs Medical Center, and the University of Texas Health Science Center compared the vaccine's effectiveness in March to that in September.

They found that the Pfizer-BioNTech vaccine’s effectiveness against infection dropped to 43.3% from 86.9% after six months. The Moderna vaccine saw a similar decline, falling to 58.0% from 89.2%. They observed the largest drop in the Johnson & Johnson vaccine, which was 13.1% effective in September compared to 86.4% in March.

Although the large decline is concerning, the researchers emphasized that the vaccines provided protection against death, even during the surge of the Delta variant. Experts say getting vaccinated against COVID-19 is still crucial because it can protect against severe outcomes such as hospitalization and death.

Vaccines Still Offer Protection

Although the protection against COVID-19 infection wanes over time and breakthrough infections cannot be prevented completely, that doesn’t mean that you shouldn't get vaccinated in the first place.

“Although vaccine effectiveness against infection decreased substantially during the Delta surge as measured in this study of Veterans, protection against death remained relatively high, particularly with the mRNA vaccines,” William Moss, MD, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health, told Verywell.

“It is important for people to be vaccinated to protect themselves against severe COVID-19, including hospitalization and death,” he added. “We can live with an infection that causes mild illness, but not with one that causes people to be hospitalized and die, and one that overwhelms our health care systems.”

The study showed that the risk of COVID-19 infection and death after infection was highest among unvaccinated veterans, which only highlights the importance of vaccination even further.

“Having some protection against COVID-19 is better than having no protection,” Scott Roberts, MD, Yale Medicine infectious diseases specialist and assistant professor of medicine at Yale School of Medicine, told Verywell. “Even in those who do get infected because of declining immunity, there is still a degree of protection against bad outcomes such as hospitalization and death.”

Should You Still Get Booster Shots?

COVID-19 vaccines remain effective against severe outcomes, but booster shots are recommended because they increase the protection afforded by vaccines, experts say.

“A booster shot will greatly increase immunity even in fully vaccinated individuals, and we recommend people who qualify, such as those greater than age 65, or those with medical problems that put them at risk for severe COVID-19, to get boosted,” Roberts said. “Even though there is still a strong protection against death, boosters will increase the chances that an infection will not occur in the first place, and may also reduce the risk of transmitting the infection to others if it does occur.”

According to the researchers of the study, vaccines remain the most important tool in preventing COVID-19 infection and death, but they should be accompanied by additional preventive measures for both vaccinated and unvaccinated people.

“Although the mRNA vaccines protect against death, some vaccinated individuals get sick and die,”  Moss said. “Booster doses will provide additional protection, along with masking, hand washing, and social distancing, until community transmission decreases to low levels and we come to live with this virus.”

What This Means For You

If you haven't gotten vaccinated yet, experts say it's your best way of protecting yourself and others against COVID-19. You can find an appointment near you here.

Will Children Need Booster Shots, Too?

Now that all children 5 and up are eligible to get vaccinated, you may be wondering whether they will be recommended to get booster shots down the line as well.

“Right now, there is not enough data to support the use of booster shots in children,” Roberts said.  “However, immunity in these age groups is constantly being monitored and it is likely that at some point in the future booster shots will be recommended.”

Booster shots may eventually be authorized for children should there be a need for them. But it's still too early to tell.

“It is likely that booster shots for children 5 to 15 years old will be needed if community transmission remains high,” Moss said. “But we will need to see the risk of breakthrough infections and disease in this age group as more children are fully vaccinated. Given the low risk of severe disease in this age group, booster doses may not be needed if community transmission goes down and the risk of infection becomes low.”

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.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. The White House. Press Briefing by White House COVID-⁠19 Response Team and Public Health Officials.

  2. Cohn BA, Cirillo PM, Murphy CC, et al. SARS-CoV-2 vaccine protection and deaths among US veterans during 2021. Science.

By Carla Delgado
Carla M. Delgado is a health and culture writer based in the Philippines.