Addendum to Ep 284 on discussion about adapted vaccines
Ep 284-13: David Khoury medRxiv 26 Aug 2022 Predicting the efficacy of variant-modified COVID-19 vaccine boosters
This paper is based on 2 sources
- the various recent preprints comparing increase in neutralization titers after booster with ancestral or variant-specific boosters.
- the previous work by Khoury where the relation between neutralization titers and protection against infection and disease was calculated, based on original phase 3 trials.
- Neutralisation titers increase after booster with
- Ancestral strain = 11 X
- Variant strain = 16.6 X ( = 1.51 X more than ancestral
- No significant difference in homologous versus non-homologous variant
- Clinical protection: in a population that is still 50 % protected against symptomatic infection and 86.6 % against severe disease because of previously acquired immunity (by vaccination and/or infection).
Additional protection by booster:
- Against symptomatic disease
- Ancestral booster: 50 → 85.6 %
- Variant booster: 50 → 90.2 %
- Against severe disease
- Ancestral: 86.6 → 98 %
- Variant: 86.6 → 98.8 %
If the basal level of protection is lower (because of waning) the additional gain of a booster is higher (up to 15 % ) and the difference between variant or ancestral booster is more important
- The main gain is by booster, but an additional gain from variant specific booster
- The importance of this additional gain depends on the basal immunity
Clearly, this modeling needs to be confirmed in clinical trials / observations
It applies only on the presently known variants.
5 Oct 2022 Episode 289: Omicron BA.2.75 revisited and the outlook for new variants, including BQ.1.1
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