A new study in the US has revealed that the Covid-19 vaccine is less effective in people with weakened immune systems.
The research from the Centers for Disease Control and Prevention’s VISION Network analysed real-world data on mRNA vaccine effectiveness during Omicron BA.4 and BA.5 predominance for immunocompromised adults.
The large, geographically diverse study confirmed that overall protection provided by vaccination — even with one or two boosters — for this population is lower than for adults without immunocompromising conditions.
Vaccine effectiveness is lowest among individuals with solid organ or stem cell transplants or hematologic malignancies such as leukaemia, lymphoma, or multiple myeloma.
The multistate study includes data from spring and summer 2022 when BA.4 and BA.5 Omicron subvariants became dominant and a total of four vaccine doses (two primary and two booster doses) was available to adults with immunocompromising conditions.
The researchers suggest that non-pharmaceutical interventions, including masks, prophylactic antibody treatment, and anti-viral treatment after acquisition of the virus are important tools to consider for additional protection against severe Covid-19 in immunocompromised adults.
Lower protection despite boosters
A review of the medical records of 30,000 immunocompromised adults found protection against Covid-19 associated hospitalisations was just 34% after two vaccine doses. This increased to 71% seven to 89 days after a third dose, then declined to 41%.
“While vaccines in the general adult population have been found to be 70-90% effective, for the immunocompromised we’re looking at a much lower range — 34-71% effective,” commented study co-author Brian Dixon, of the Regenstrief Institute and Indiana University Richard M. Fairbanks School of Public Health.
“Those with healthy immune systems should keep in mind that we are a community with a responsibility to keep fellow community members, who are immunocompromised or have other conditions that place them at higher risk for Covid, even with vaccination, protected by taking precautions like hand hygiene and mask wearing, especially when transmission rates are high. We need to look out for one another,” he added.
