07 March 2022

Immunocompromised patients should receive additional COVID-19 vaccines, experts have recommended.

The findings, published in the latest edition of The BMJ, confirms the importance of additional doses of COVID-19 vaccine to protect people with a weakened immune system, including people with blood cancers.

Researchers in Singapore analysed the results of 82 observational studies conducted worldwide, to compare the effectiveness of COVID-19 vaccines in immunocompromised and immunocompetent people.

Of these studies, 77 (94%) used mRNA vaccines, 16 (20%) viral vector vaccines, and 4 (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.

After one COVID-19 vaccine dose, seroconversion was found to be reduced among immunocompromised groups, except people with HIV.

Seroconversion rates were less than half as likely in people with blood cancers (40% seroconversion compared to immunocompetent controls). Seroconversion rates were also roughly half as likely in people with immune mediated inflammatory disorders, such as rheumatoid arthritis and psoriasis, and solid cancers. Organ transplant recipients were 16 times less likely to seroconvert.

A second dose significantly increased seroconversion in patients with blood cancers, to 63% compared to immunocompetent controls. Similar increases were observed in people with immune mediated inflammatory disorders and solid cancers. However, still only one third of transplant patients achieved seroconversion.

A further review of 11 studies showed that a third dose of a COVID-19 mRNA vaccine was associated with seroconversion among vaccine non-responders with solid cancers, blood cancers, and immune mediated inflammatory disorders. However, results showed a varied response in transplant recipients. No published evidence was available for people with HIV.

Although the included studies were observational and used different definitions of seroconversion, the research team believe that stringent study inclusion criteria, as well as rigorous and systematic evaluation of study quality, mean their conclusions are robust.

Source: Lee ARYB, Wong SY, Chai LYA, Lee SC, Lee MX, Muthiah MD, Tay SH, Teo CB, Tan BKJ, Chan YH, Sundar R, Soon YY. (2022) “Efficacy of COVID-19 vaccines in immunocompromised patients: systematic review and meta-analysis.” BMJ, doi: 10.1136/bmj-2021-068632.

Link: https://www.bmj.com/content/376/bmj-2021-068632

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