A factory-made antibody called nirsevimab has proven safe and effective at reducing the risk of severe RSV infections in babies
27 February 2023
Parents with babies could soon be offered an antibody injection around the start of winter that will help protect their child against the respiratory syncytial virus over the entire season, when RSV infections peak. There is currently no option available for protecting healthy babies against the virus, which can cause serious and sometimes deadly infections in infants less than a year old.
A trial involving 3000 infants has shown that this factory-made antibody, called nirsevimab (Beyfortus), is safe and reduces the risk of babies needing medical attention for severe RSV infections by 79 per cent over the 150 days after the injection. It reduces the risk of hospitalisation by 77 per cent over the same period. The results were presented at a conference on RSV in Lisbon, Portugal, on 23 February.
“This is very special, because there’s been a search for a vaccine or something to prevent RSV disease in healthy infants,” says Tonya Villafana at AstraZeneca, who led the development of nirsevimab. “They can get very sick.”
There is no RSV vaccine that provokes an effective immune response in babies and may never be, says Villafana. But injecting antibodies can provide protection for as long as they remain in the bloodstream.
The hope is that nirsevimab will be available ahead of the next northern hemisphere winter, but it will be up to individual countries to approve it, says Villafana.
In older children and adults, RSV infections typically cause no more than cold symptoms, but in the very young and very old, infections can be much more serious. Around 100,000 children die from RSV every year worldwide. In high-income countries, deaths are rare, but many babies require medical care because of RSV.
At present, there is no approved RSV vaccine. There is a protective antibody called palivizumab (Synagis), but it requires multiple injections over the RSV season, as it doesn’t remain in the body for long. As a result, it is given only to vulnerable babies such as those born prematurely. Nirsevimab has modifications that slow its breakdown in the body, so its protective effect lasts much longer, says Villafana.
Nirsevimab has already been approved as a preventative treatment for all babies – not just vulnerable ones – in the EU and the UK on the basis of initial results from the first 1500 babies. Other countries, such as the US, have been waiting for the full trial results, says Villafana.
As the full results are slightly better than the initial ones, it is now likely that nirsevimab will be approved in many countries around the world.
However, cost will be a major issue in determining how widely nirsevimab is used globally. Antibody treatments tend to be extremely expensive because they are difficult to manufacture and medical authorities in some countries won’t recommend the use of nirsevimab if the cost is too high. AstraZeneca hasn’t yet announced pricing.
In England, nirsevimab would have to be priced around £60 per dose or less to be cost-effective, according to an estimate by Katherine Atkins at the London School of Hygiene & Tropical Medicine and her colleagues.
“We are calculating the highest price per dose that England should be willing to purchase nirsevimab for,” says Atkins.
In lower-income countries, the price would have to be even lower. In Vietnam, for instance, the price would have to be around $5 for it to be cost-effective, says Lien Anh Ha Do at the Murdoch Children’s Research Institute in Australia.
Sign up to our free Health Check newsletter that gives you the health, diet and fitness news you can trust, every Saturday
More on these topics: