New RSV vaccines and treatments combat rising threat in infants and seniors

Emerging RSV vaccines and therapies are reshaping protection strategies amid earlier and more severe outbreaks, especially targeting vulnerable infants and older adults as global cases increase.

Respiratory syncytial virus, or RSV, is usually known for causing cold-like symptoms, but it can pose a far greater threat to infants, older adults and people with underlying health problems. The European Medicines Agency says RSV is especially dangerous in babies under six months old and is responsible for the great majority of infant lung infections during peak seasons. It also estimates that, in 2019, the virus caused millions of hospital admissions and more than 100,000 deaths in children under five worldwide.

The concern has sharpened because infections have been rising earlier than usual this year, with more young children being admitted to hospital than in previous seasons. A study published in The Lancet found that one in 56 otherwise healthy babies in Europe is being hospitalised with RSV. Some experts have suggested that reduced exposure to common viruses during Covid-19 lockdowns may have left immune systems less prepared, helping to fuel the surge.

The race to develop protection has been long and difficult. Work on an RSV vaccine began in the 1960s, but early efforts were set back after one candidate caused serious illness and, in two infants, death. That history kept researchers cautious for decades, even as the virus continued to drive winter surges in illness. Today, however, governments and public health officials are warning about a possible “tripledemic” of Covid-19, influenza and RSV, and manufacturers have advanced several products through late-stage testing and regulatory review.

For older adults, the field has already moved into routine use in some markets. The US Food and Drug Administration approved Arexvy as the first RSV vaccine for adults aged 60 and over, and also for some younger adults at increased risk. Another option, mRESVIA, has also been approved for older adults and certain high-risk younger people. GSK’s vaccine, the first aimed at this age group, has already been approved in Japan, with decisions in the US and European Union expected later. Moderna has also been developing a combined Covid-19, flu and RSV shot, although that programme has drawn criticism because it was promoted before Phase III trials were complete.

Protection for infants is being pursued through different strategies. Pfizer has developed a vaccine for use in pregnancy, given in the second or third trimester so that antibodies pass to the fetus before birth. Clinical trials have found it to be 82% effective at preventing severe RSV in babies under three months old, and the company is preparing to seek approval from the US Food and Drug Administration. In Europe, two RSV products are already approved: Beyfortus, a single-dose monoclonal antibody developed by Sanofi and AstraZeneca for newborns and infants, and Synagis, a long-established preventive treatment sold by Orphan Biovitrum.