Why's there no vaccine against Respiratory Syncytial Virus (RSV)?

Question

RSV was discovered in 1956. Here’s why we can’t rush a COVID-19 vaccine | AAMC

Respiratory syncytial virus (RSV): This pervasive respiratory virus has proven resistant to vaccination. Children treated with one vaccine in the 1960s developed an enhanced form of the disease, suffering high fever, bronchopneumonia, and wheezing. Many were hospitalized and two died.

“That set the field back years,” Poland said, as researchers and manufacturers “were afraid” to try again.

Researchers have since tried but still not developed an RSV vaccine for public use, according to the CDC. Babies at particularly high risk for RSV are sometimes injected with an antibody to help fight off infection.

I don't grasp the Canadian government's Overview of the respiratory syncytial virus vaccine candidate pipeline in Canada, CCDR 46(4). E.g. so what if "amino acids do vary in prefusion specific epitopes"?

Challenges to RSV vaccine development

Antigen diversity

A successful vaccine candidate will account for the diversity of antigens presented by RSV in the form of the structural variability of the proteins on the surface of the virus. The protective, neutralizing antibody response to RSV is dominated by antibodies targeting the prefusion F protein on the surface of RSVFootnote 17Footnote 18. Although the genetic sequence of F does not vary substantially between strains of RSV [89% of its sequence is identical in both A and B strainsFootnote 19], amino acids do vary in prefusion specific epitopes [bolding mine]. As new products are authorized and make it into broad usage, it will be critical to understand the sero-epidemiological responses at a population level to understand whether prefusion or postfusion antibodies are dominant responses, and whether these demonstrate equivalent protection against both RSV type A and B.

RSV infection dampens the immune response

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There are no clear correlates of protection

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Answer 1

In answer to the specific question, This paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3741363/ is the one the review was talking about.

The epitope that is targeted (the F protein) varies between strains, so a produced vaccine would only work on that strain. The protein (an obvious vaccine target) was selected because it exists on all strains, and is needed for the virion to fuse with the human cell.

In the vaccine The F protein epitope is fused with an immunostimulatory particle to get a good immune response. That's why they mention "prefusion" and "postfusion". There is confusion in the terminology because the F protein is so-named because of its role in fusing the virion to the cell.

Answer 2

RSV has been a difficult virus to create a vaccine against, though an experimental vaccine has finally been developed and is being tested by the University of Texas at Austin. Your article with Canada is probably talking about how certain amino acids and antibodies seem to be effective against the virus. However, this virus is a strange beast that is hard to treat. A potential vaccine was tested in the 1960s, but all it did was increase the rate of infection for the RSV, leading to some scientists classifying RSV as "immunopotentiation" or vaccine-enhanced. Normally, a vaccine contains a dead version of the virus or weakened byproducts of the virus to create a strong immune response to defeat a virus. However, with RSV, this process tends to make the viral infection worse. Hopefully, this new vaccine will yield results (and even if it doesn't, a medication called palivizumab can be given to babies and children to protect against the virus).