Do immunocompromised people need a third dose of the COVID-19 vaccine?


A. Maybe. Emerging data suggest that a third dose of COVID-19 vaccine can induce a better immune response in some immunocompromised people.

The CDC is expected to meet in the near future to discuss a possible 3-dose vaccine regimen for immunocompromised people. In the meantime, the CDC has stated that the current vaccine regimen may not induce a sufficient immune response in SOME immunocompromised people and has advised continued masking and maintaining physical distance to stay safe.

➡️TL;DR. Recent data indicate that a third dose of COVID-19 vaccine (mRNA or adenovirus-based) may improve the weak immune response in some immunocompromised people. While these data are encouraging, there is no formal guidance as yet regarding a 3-dose regimen. People who are immunocompromised should discuss the question of a third dose with their doctor and continue to take precautions against COVID-19.

❓ Why the discussion? While COVID-19 vaccines induce remarkably robust immune responses in healthy people, some immunocompromised people do not make good responses to these vaccines. These people remain at high risk for COVID-19. Breakthrough infections following vaccination have occurred in immunocompromised people. In one report, 14 solid organ transplant recipients were diagnosed with COVID-19 approximately 23.5 days following vaccination. 50% of this group required hospitalization, one person died, and 2 had prolonged hospital stays. An Israeli study that reported breakthrough infections following vaccination in 152 people noted that 40% of them were immunocompromised and most of them had comorbidities such as high blood pressure, kidney or lung disease, cancer, or heart failure.

People may be immunocompromised because (1) they have had an organ transplant and are on immunosuppressive medicines, (2) they have an inherited defect of their immune system, or (3) they are on treatment for certain types of cancers (notably cancers of blood cells). Many of these people have received COVID-19 vaccines. Reports suggest that approximately 20% of these people develop an antibody response to vaccination, while the rest have either a very weak or no response.

❓ Will a third dose of the vaccine help? Researchers studied this question in a group of 101 people who had received organ transplants (liver, kidney, lung, heart or pancreas). All 101 had received both doses of the Pfizer vaccine and approximately 50% had no antibody response. All 101 people were given a third dose of the vaccine approximately 61 days after the second dose. Approximately 40% of the people who had previously not made an antibody response to the Pfizer vaccine, now had antibodies. The people who had antibodies following the first 2 doses had higher titers of antibody after the third dose. There still were some people who did not make an antibody response even after the third vaccine dose.

A second study evaluated a third dose of either Pfizer, Moderna or J&J vaccine after the standard 2-dose Pfizer or Moderna vaccine. Of the 50 patients evaluated in this study, about a third who were antibody negative after the first 2-dose vaccine, developed an antibody response after the third dose. Again, not all patients developed antibodies after the third vaccine dose.

While the majority of studies thus far have reported the lack of or weak antibody response to COVID-19 vaccines in immunocompromised people, it is important to remember that the immune response is complex and includes not just antibodies, but T cells as well. T cells are a critical part of the protective immune response. Healthy people develop COVID-19 vaccine-specific T cells following vaccination. Ongoing research studies are addressing the question of COVID19 vaccine-specific T cell responses in immunocompromised people.

❓ Will a 3-dose regimen be recommended for immunocompromised people? These data are encouraging, but preliminary. The CDC is expected to meet in the near future to discuss the benefit of a third dose in certain groups of immunocompromised people. In the meantime, people who are immunocompromised for a variety of reasons are advised to continue to wear masks and practice social distancing to minimize their risk for COVID-19.

👍🏽 Bottomline: A 3-dose vaccine regimen for immunocompromised people has shown encouraging results for some people but is not formal guidance as yet. Continue to stay safe by masking, hand washing and distancing!

Those Nerdy Girls

📚 Additional reading:

CDC guidance for immunocompromised people

CDC meeting regarding possible third vaccine dose

Breakthrough infections in immunocompromised people:

Transplant Journal Article
News Medical Life Sciences

The variable vaccine response in immunocompromised people

T cell response to COVID-19 vaccines

Three doses of Pfizer vaccine in organ transplant recipients

Third dose of Pfizer, Moderna or J&J in organ transplant recipients

Dear Pandemic post on COVID-19 vaccines and immunosuppression

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