RSV and shingles vaccines: antibody responses preserved with simultaneous administration

Two vaccines, together or one month apart

This phase III trial compared the prefusion F protein RSV vaccine with the AS01E adjuvant and the recombinant shingles vaccine with the AS01B adjuvant. Participants were randomly assigned to two groups of 265 people. The trial was open-label: vaccination allocation was not masked.

One group received both vaccines on the first day. The other received the shingles vaccine first, followed by the RSV vaccine one month later. All participants received the second dose of the shingles vaccine on day 61. The primary endpoint concerned the antibody response, while safety and post-vaccination reactions were secondary endpoints.

Comparable antibodies according to the predefined threshold

The researchers measured neutralizing antibodies against RSV subtypes A and B, as well as antibodies against glycoprotein E of the virus responsible for shingles. All three comparisons met the non-inferiority criterion defined before the analysis.

This means that simultaneous administration did not reduce the antibody response beyond the margin accepted in this trial. It demonstrates neither strictly identical responses nor equivalent protection against infections, complications or hospitalizations: the abstract does not report these clinical outcomes.

More reactions after the combined visit

Within seven days of the first visit, administration-site reactions were reported by 71.7% of the group receiving both vaccines, compared with 58.5% of the group receiving only the shingles vaccine. Systemic reactions affected 73.6% and 60.4% of participants, respectively.

These percentages compare a visit involving two vaccinations with a visit involving only one. They therefore do not allow the conclusion that simultaneous administration causes more reactions over the entire vaccination schedule.

No fatal adverse events or serious events considered related to vaccination were reported. With 530 participants, this observation is not sufficient to rule out rare adverse effects.

A useful finding, not a general recommendation

The trial supports the possibility of administering these two formulations together in terms of antibody responses. On its own, it is not sufficient to determine who should receive these vaccines or to change the recommendations applicable in France. The dossier contains no regulatory source that would settle these questions.

What we can take away

For these two specific vaccines, simultaneous administration meets the non-inferiority criteria for antibody responses. Equivalent clinical protection remains distinct from this immunological finding.