Since March 2020, the COVID-19 infection has ravaged the planet, killing over five million people and infecting hundreds of millions more. In addition, the rapid spread of SARS-CoV-2 prompted governments to impose considerable restrictions on socializing, travel bans, and the closure of businesses and schools in an effort to stop the virus from spreading further.

However, the arrival of many SARS-CoV-2 vaccines, particularly those based on the messenger ribonucleic acid (mRNA) platform, has provided hopes for a return to normalcy if vaccine coverage is reached quickly and completely.

The Centers for Disease Control and Prevention (CDC) in the United States has reported on the efficacy of mRNA vaccinations against SARS-CoV-2 among immunocompromised people.

Due to underlying medical disorders or the use of certain drugs, immunocompromised individuals have weak humoral or cellular immunity. Due to the lower robustness of their immune responses, this minority of patients may not gain as much from COVID-19 vaccines as the immunocompetent.

Immunocompromised people, who make up roughly 3 percent of the adult population in the United States, were studied using data from the VISION Network on hospitalizations among adults with COVID-19-like illness. From January 17 through September 5, 2021, roughly 190 hospitals in nine US states were covered.

The researchers analyzed hospitalization rates in two groups of people who had received two doses of an mRNA vaccine, the second shot given 14 days or more before the hospitalization. Over 20,000 immunocompromised individuals were in the initial group, with over half (53 percent) of them being fully vaccinated. The second study included almost 69,000 immunocompetent adults, with 43 percent having received all vaccines.

Both groups had similar median ages, at 68 and 70 years old, respectively. Pfizer and Moderna vaccines had been given to about 60 percent of each group. In both groups, the median time between the second dose and hospitalization was around 90 days.

In 29 percent of the immunocompetent cohort, SARS-CoV-2 infection was verified by molecular testing. Approximately a quarter of the sample were infected without being vaccinated, while 4 percent were adequately vaccinated but got breakthrough infections. About 16 percent of the immunocompromised were infected, with 12 percent of those who were unvaccinated and 4 percent of those who were fully vaccinated becoming sick.

After taking into account differences in age, location, time in the research period, and predominant SARS-CoV-2 strain in the local community, vaccine efficacy (VE) was calculated based on probabilities of testing positive for SARS-CoV-2 if vaccinated or unvaccinated.

In the first cohort, the VE against COVID-19-related hospitalizations was 77 percent, whereas in the immunocompetent group, the VE was 90. In terms of the vaccination product, Moderna and Pfizer vaccines had VE of 81 percent and 71 percent, respectively. Another factor that had no effect on results: patient age and circulating variants at the time of admission.

The VE was 76 percent and 79 percent in the immunocompromised before and after the Delta mutation became dominant, compared to 91 percent and 90 percent in the immunocompetent. Organ and stem cell transplant recipients had the lowest VE, while those with rheumatoid arthritis or chronic inflammation had the highest VE.

Immunocompromised patients are less likely to benefit from the mRNA vaccines and are more likely to require hospitalization from COVID-19 disease. Variations in the VE can be seen within this subset of people depending on the specific causes of the underlying disorder.

Nonetheless, the proven protection provided by vaccines to immunocompromised people is critical. To prevent severe sickness if infected with SARS-CoV-2, a third dose of the vaccine should be given, especially to people with moderate to severe immunocompromise.

Some immunocompromised people are at more risk than others, and these patients account for a higher proportion of COVID-19-related hospitalizations.

Image Credit: Getty

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