New Study: Pfizer and Moderna Shots Are Less Effective in People with Lowered Immune Systems
For months, the medical community has been abuzz about how the COVID-19 vaccine is less effective for the immunocompromised population (people with compromised or lowered immune systems). And now, there’s new research to support it.
A study published in the Centers for Disease Control and Prevention (CDC)’s Morbidity and Mortality Weekly Report this week analyzed the effectiveness of the mRNA Pfizer-BioNTech and Moderna COVID-19 vaccines in 20,101 people across nine states with weakened immune systems, between January and September 2021. Of that number, 10,564 people were fully vaccinated. That data was compared with 69,116 adults with normal immune systems, 29,456 of which were fully vaccinated.
The researchers found that the effectiveness of the mRNA vaccines against laboratory-confirmed cases of COVID-19 was 77% in immunocompromised patients, compared to 90% efficacy for those with typical immune systems.
But not all immunocompromised people even reached a 77% effectiveness, the researchers pointed out, noting, “vaccine effectiveness varied considerably among immunocompromised patient subgroups.” Specifically, people who had organ or stem cell transplants were more likely to have a 59% efficacy, while those who had a rheumatic or inflammatory disorder like rheumatoid arthritis saw efficacy numbers up to 81%.
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“These findings are important, but not surprising,” says William Schaffner, M.D., an infectious-disease specialist and professor at the Vanderbilt University School of Medicine. Infectious disease expert Amesh A. Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security, agrees. “Immunocompromised people are used to the fact that vaccines, which stimulate the immune system, are not going to be as effective in them as in someone who has a more robust immune system,” he says.
As a result, “they just don’t have optimal protection from the vaccines,” says Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York.
If you’re immunocompromised or have a loved one who is, you likely have questions. Here’s what you need to know.
What does it mean to be immunocompromised?
When someone is immunocompromised, it means that they have a weakened immune system, according to the CDC. That can include people with HIV/AIDS, cancer, those who have had organ transplants, people on immunosuppressive medications, and patients who have inherited diseases that impact their immune system.
There is a range with immunosuppression, though, and that’s why there is a broad range in how effective the COVID-19 vaccine is for this group, Dr. Russo says. People who are moderate to severely immunocompromised make up about 3% of the adult population, the CDC says.
What are the current vaccine recommendations for people who are immunocompromised?
The CDC currently recommends that people who have moderately to severely compromised immune systems get a third dose of an mRNA vaccine at least 28 days after their second dose.
The CDC cites research that has found that some immunocompromised people don’t always create the same level of immunity after getting vaccinated the way other people do and may benefit from an additional dose to ensure adequate protection against COVID-19. The CDC also refers to a study that found fully vaccinated immunocompromised people make up a large proportion of people hospitalized with breakthrough cases (where they get infected with COVID-19 despite being fully vaccinated).
But getting a third dose isn’t a guarantee that immunocompromised people will have the same level of protection as others. “Even after the third dose, immunocompromised people should recognize that they are more vulnerable than their friends and relatives,” Dr. Schaffner says.
That’s why he recommends that people who are immunocompromised wear masks in public, do their best to social distance, and avoid large groups whenever possible.
There is a chance that the CDC will eventually recommend a fourth shot for people who are immunocompromised, Dr. Russo says, but that’s unlikely to happen before the new year.
In the meantime, AstraZeneca has requested that the Food and Drug Administration grant an emergency use authorization for its long-acting antibody treatment to prevent COVID-19 in people who are at high risk of the virus. “That may be useful in protecting people from COVID who don’t mount great responses to the vaccine,” Dr. Adalja says.
Should you take an antibody test if you’re immunocompromised?
Though antibody tests seem like a great indicator of someone's immune response to the vaccine, that's not always the case. It’s not currently recommended for immunocompromised people to get them. “Antibody tests are unreliable,” Dr. Schaffner says. “We hope they will improve in the future but at the moment, they’re not recommended.”
Dr. Adalja agrees. “Some individuals are getting antibodies measured, but it’s very hard to actually make that data actionable because we don’t know the correlation of protection,” he says. “Obviously if the value is zero, that’s one indication of lack of protection.” But, he points out, antibody tests “ignore” T-cell immunity, which is another element in your overall protection against the virus. “Antibody tests are really not something that is useful for this type of purpose in a general sense,” he says.
If you're not sure if you qualify as being immunocompromised, Dr. Russo recommends talking to your doctor—they should be able to offer insight. Still, he says, it's a good idea to get a third shot if you're unsure. "There's a low threshold here," he says. "When in doubt, get that extra shot."
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