Key messages

• Respiratory syncytial virus (RSV) prefusion vaccines reduced RSV illness in older adults. When pregnant women received RSV F protein-based vaccines, their babies had fewer serious RSV illnesses. This was true for both approved and unapproved vaccines.

• The effectiveness of RSV vaccines in women of childbearing age and the impact of live RSV vaccines on infants and children remain uncertain. These trials used unapproved vaccines.

• Further research is needed looking at RSV vaccines in women of childbearing age and the effects of live vaccines on infants and children.

What is respiratory syncytial virus (RSV)?

RSV is a virus that spreads easily and causes respiratory illnesses. Most people get it when they are very young, and nearly all have had it by the age of two.

How is RSV prevented?

It can be prevented by getting vaccinated, using special antibodies, washing hands, and avoiding close contact with sick people.

What did we want to find out?

We wanted to know how well RSV vaccines work in preventing RSV and how safe they are.

What did we do?

We searched for studies that compared RSV vaccines to placebo (dummy treatment), no treatment, vaccines for other respiratory infections, other RSV vaccines, or monoclonal antibodies (lab-made proteins that help the immune system fight disease) in all people. We compared and summarised the results of the studies and rated our confidence in the evidence based on factors such as study methods and sizes.

What did we find?

We found five studies on older adults, three on the effect of vaccinating pregnant women on their babies, one on women of childbearing age, and five on infants and children.

Main results

RSV prefusion vaccine versus placebo in older adults; 4 studies (99,931 people)

RSV prefusion vaccines reduced RSV-related respiratory illness by 77% and RSV-related acute illnesses by 67% in older adults. We are confident in these results.

There may be little to no difference between RSV prefusion vaccine and placebo in numbers of serious unwanted effects, people who die from RSV itself, or people who die from any cause. We have low confidence in these results.

The studies did not report RSV-related hospitalisation or intensive care unit (ICU) admission.

RSV postfusion F protein-based vaccine versus placebo in older adults; 1 study (1894 people)

There is probably little to no difference between RSV postfusion F protein-based vaccine and placebo in RSV-related respiratory illness or RSV-related acute illnesses in older adults.

There may be little to no difference between RSV postfusion F protein-based vaccine and placebo in numbers of serious unwanted effects, people who die from RSV itself, or people who die from any cause. We have low confidence in these results.

The study did not report RSV-related hospitalisation or ICU admission.

Maternal RSV F protein-based vaccine versus placebo in infants; 3 studies (12,010 people)

Maternal RSV F protein-based vaccine reduced RSV-related respiratory illness by 54%, severe RSV-related respiratory illness by 74%, and hospitalisations due to RSV by 54% in infants. We are confident in these results.

There may be little to no difference between maternal RSV F protein-based vaccine and placebo in numbers of serious unwanted effects, infants who die from RSV itself, or infants who die from any cause. We have low confidence in these results.

The studies did not report ICU admission.

Live-attenuated RSV vaccines versus placebo in infants and children; 5 studies (192 infants and children)

We are uncertain if live RSV vaccines reduce respiratory illnesses and RSV-related illnesses in infants and children.

There may be little to no difference between live RSV vaccines and placebo in numbers of serious unwanted effects.

The studies did not report RSV-related hospitalisation, numbers of infants and children who died from RSV itself, numbers who died from any cause, or ICU admission.

RSV recombinant F nanoparticle vaccine versus placebo in women of childbearing age; 1 study (300 women)

We are uncertain if RSV recombinant F nanoparticle vaccine prevents new RSV infections in women of childbearing age.

There may be little to no difference between RSV recombinant F nanoparticle vaccine and placebo in numbers of serious unwanted effects, people who die from RSV itself, or people who die from any cause. We have low confidence in these results.

The study did not report RSV-related hospitalisation or ICU admission.

What are the limitations of the evidence?

We only included articles published in English, and therefore may have missed studies published in other languages. There were occasional issues with the way some studies were done, but overall the studies were well conducted.

How up-to-date is the evidence?

The evidence is current to April 2024.