As Covid-19 infections have continued to rise in recent weeks, increasing hospital admissions combined with staff sickness are placing an increased strain on health systems around the world. Recent research published by the US Centres for Disease Control and Prevention (CDC) has shown that immunocompromised people face an increased risk of intensive care unit (ICU) admissions and death due to illness associated with Covid-19. It is important that we closely monitor transmission levels in immunocompromised groups to minimise severe illness and mortality.

The study, published by Singson and colleagues, analysed data on adults aged older than 18 years who had been hospitalised with Covid-19 across ten US states to explore associations between immunocompromised status, ICU admissions and deaths between March 2020 and February this year. People are considered to be immunocompromised if they have a weakened immune system due to several types of conditions. This includes those treated with drugs suppressing the immune response, those receiving cancer treatment or an organ transplant, and those with advanced or untreated HIV infections. According to GlobalData epidemiologists, around 13% of prevalent HIV cases in the US were undiagnosed this year. These individuals that are not receiving treatment for the condition are particularly susceptible to severe Covid-19 outcomes and transmission should be monitored in this group.

The study found that among unvaccinated patients, immunocompromised people were at a 26% higher risk of ICU admission and an 87% increased risk of in-hospital death compared to non-immunocompromised individuals. Furthermore, immunocompromised people were at higher risk of adverse outcomes even if they had been fully vaccinated. Among vaccinated patients, immunocompromised patients had a 42% higher odds of death compared to non-immunocompromised patients. As well as reinforcing the importance of Covid-19 vaccination in preventing severe health outcomes, these findings highlight the additional risks of Covid-19 faced by immunologically vulnerable groups.

According to the World Health Organisation (WHO), fueled by the spread of BA.4 and BA.5 Omicron subvariants, Covid-19 incident cases have tripled over the last six weeks. Rising case numbers have been mirrored by a substantial increase in hospitalisations. Fortunately, ICU admissions for Covid-19 remain at low levels at present, but as infection rates among older age groups continue to increase, Europe is still observing around 3,000 deaths a week. The WHO has urged countries to consider mitigation measures now to prevent overwhelming health systems in the coming autumn and winter.

As many of the Covid-19 restrictions imposed earlier in the pandemic are no longer enforced in much of the world, it is ever more important that immunocompromised people seek out additional protection measures during this period of high Covid-19 transmission. This includes non-pharmaceutical interventions such as mask-wearing and social distancing, up-to-date vaccination of immunocompromised people and their close contacts, and early testing and uptake of early antiviral treatments in order to reduce their risk of severe Covid-19.