Optimal booster timing for RSV and COVID

Both wane; exactly how often to re-dose for the best protection is still being refined as data accrue.

How much these prevent versus delay in the very elderly

Trial efficacy is clear; the long-run population benefit in the oldest and frailest is still being studied.

Adult vaccines, honestly — the evidence, not the argument

Adult vaccines are among the best-evidenced preventive tools in medicine — some (shingles, RSV) show strong trial efficacy, others (flu) are modest and year-variable. This is educational, not a schedule: your specific vaccines and timing should come from your clinician and current guidance.

How to read this

This is not advocacy and not a schedule — it’s the honest state of the trial evidence, so you can have a better conversation with your clinician. Efficacy figures are from the pivotal trials; real-world effectiveness is usually somewhat lower, and recommendations (especially for COVID and pneumococcal) change over time.

The strongest evidence

High trial efficacy.

Shingles (recombinant zoster, Shingrix) — One of the strongest adult-vaccine signals: about 97% efficacy against shingles in adults 50+ and ~90% in those 70+. Two doses; a sore arm and short-lived fatigue are common. (established)
RSV vaccine for older adults — In first-season trials the RSV vaccines cut RSV lower-respiratory disease by ~83–89% in older adults. Two-season figures are lower, consistent with waning — so timing matters. (established)

Real, but more modest or nuanced

Flu vaccine — real but modest, and year-variable — A Cochrane review in healthy adults found it cut the chance of flu from about 2.3% to 0.9% (you’d vaccinate ~71 people to prevent one case). It depends on how well the vaccine matches the season’s strains. In older adults, high-dose formulations are ~24% more effective than standard dose. (note)
Pneumococcal — cuts vaccine-type pneumonia, not all pneumonia — In a large trial of adults 65+, the conjugate vaccine cut vaccine-type pneumonia (~45%) and invasive disease (~75%), but did not reduce all-cause pneumonia. Newer combinations (PCV20/PCV15 ± PPSV23) are now used. (note)
COVID — strong for severe disease, wanes for infection — Vaccines strongly reduce severe COVID, hospitalisation and death; protection against catching it wanes, which is why updated boosters are offered periodically, especially for people 65+ and the immunocompromised. Recommendations keep evolving. (note)
Tdap — tetanus/diphtheria/whooping cough — One Tdap then a booster every ten years; a dose in each pregnancy protects the newborn from whooping cough. Long-established. (established)

What we still don’t know

Optimal booster timing for RSV and COVID Both wane; exactly how often to re-dose for the best protection is still being refined as data accrue.
How much these prevent versus delay in the very elderly Trial efficacy is clear; the long-run population benefit in the oldest and frailest is still being studied.

Key terms

Efficacy vs effectiveness Protection under trial conditions versus in the messy real world — the latter is usually lower.
Recombinant vaccine Made from a lab-produced protein piece rather than a whole germ (e.g. Shingrix, Arexvy).
Herpes zoster Shingles — a painful rash from reactivated chickenpox virus, more common and severe with age.
Conjugate vs polysaccharide (PCV/PPSV) Two pneumococcal vaccine types: conjugate gives stronger, longer memory; polysaccharide covers more strains but more weakly.
Waning immunity The expected decline in protection over time — the reason boosters exist.
ACIP The US advisory committee that sets vaccine recommendations, which change as evidence evolves.