About 3% of adults in the U.S. have a condition that suppresses their immune system, which raises concerns that they might not receive as much protection from mRNA-based coronavirus vaccines.

A nine-state study released by the CDC bears that out.

The analysis of 89,000 adults from Jan. 17–Sept. 5, 2021, found full vaccination with Pfizer or Moderna was 90% effective at keeping people with conventional immunity out of the hospital, but only 77% effective among people who were immunocompromised.

The pattern held true regardless of mRNA vaccine used, age group, timing of hospitalization or prevalence of the delta variant in the relevant state.

Effectiveness varied within that group, from 59% for transplant recipients to 81% among people with inflammatory disorders.

The findings support CDC guidelines that people with such conditions receive three doses and practice precautions like masking and distancing. If infected, they should be monitored closely and given early access to treatments, such as monoclonal antibodies, that reduce disease severity.