Investigators advise third short for patients with weakened immune system, especially organ transplant recipients.
Additional doses, such as a third booster, of COVID-19 vaccines are recommended for individuals who are immunocompromised, especially for those who are organ transplant recipients and least likely to make antibodies to fight off the coronavirus, according to study results published in The BMJ.
The findings reinforce the importance of additional doses of COVID-19 to protect individuals with a weakened immune system.
Individuals who are immunocompromised are less able to make antibodies to fight off viruses, such as influenza, than individuals with healthy immune systems, but there is little known about the response to COVID-19 vaccines, especially mRNA vaccines.
To address the gap in knowledge, investigators in Singapore analyzed the results of 82 observational studies that compared the effectiveness of COVID-19 in individuals who are immunocompetent with those who are immunocompromised.
Of these studies, 77, or approximately 94%, used mRNA vaccines; 16, or approximately 20%, viral vector vaccines; and 4, or approximately 5%, inactivated whole virus vaccines. A total of 63 studies were assessed to be at low risk of bias and 19 at moderate risk of bias.
The results of the analysis showed that after 1 COVID-19 vaccine dose, seroconversion, the process of making antibodies after infection or vaccination, had been reduced among immunocompromised groups, except individuals with HIV.
The seroconversion rates were about half as likely in individuals with blood cancer, immune-mediated inflammatory disorders, including psoriasis and rheumatoid arthritis, and solid tumor cancers compared with immunocompetent controls.
Individuals with organ transplants were 16 times less likely to seroconvert.
Additionally, after a second dose, seroconversion increased significantly for individuals with blood cancer, immune-mediated inflammatory disorders, and solid cancers but remained severely reduced in transplant recipients.
Just one-third of transplant recipients achieved seroconversion.
After a review of 11 studies, a third dose of a COVID-19 mRNA vaccine was associated with seroconversion among vaccine non-responders with blood cancers, immune-mediated inflammatory disorders, and solid cancers.
However, the response varied among individuals who had received organ transplants. There was also no evidence available on the effectiveness of a third dose in individuals with HIV.
Among those in the immunocompromised groups studies, the antibody levels were also lower than in the immunocompetent controls.
Investigators noted several limitations of the analysis: The included studies were observational and used different definitions of seroconversion, which could affect the outcome.
Investigators also said they could not rule out the possibility of other unmeasured factors, such as age and underlying conditions, that may have affected the results.
The use of selective study inclusion criteria combined with rigorous and systematic evaluation of the study quality helped investigators conclude that their findings were robust.
They concluded that the seroconversion rates and antibody titers after COVID-19 vaccines are significantly lower in individuals who are immunocompromised and a third dose, as well as other targeted interventions, should be performed to further protect that group of individuals.
Study suggests additional covid-19 vaccine doses for immunocompromised patients. EurekAlert. News release. March 2, 2022. Accessed March 3, 2022. https://www.eurekalert.org/news-releases/944985