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参考資料３ WHO Statement on the antigen composition of COVID-19 vaccines (3 ページ)
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| 公開元URL | https://www.mhlw.go.jp/stf/shingi2/newpage_00104.html |
| 出典情報 | 厚生科学審議会 予防接種・ワクチン分科会 研究開発及び生産・流通部会 季節性インフルエンザワクチンの製造株について検討する小委員会（第2回 5／29）《厚生労働省》 |
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SARS-CoV-2 continues to circulate and evolve: there are genetic changes in
important regions of the spike protein of SARS-CoV-2.
As of April 2024, nearly all (>94%) SARS-CoV-2 genetic seduences in Dublicly
available databases are derived from」N.1, and these variants continue to displace
existindg XBB lineage variants (e.q. EG.5). This displacement indicates greater
fitness of」N.1 derived variants as compared to other circulating SARS-CoV-2
variants in the human population.
Several 」N.1 derived variants (e.d.」N.1.13.1,」N.1.11.1, KP.2) have independently
evolved changes in the spike protein at epitopes involving amino acid residues
346 and/or 456. Substitutions at these amino acid residues have been identified in
previous SARS-CoV-2 variants (e.q. R346T in BQ.1 and XBB: F456L in EG.5 and
HK.3) and are within epitopes known to be targeted by neutralizing antibodies.
Given the displacement of XBB lineage variants by」N.1 derived variants, it is likely
that in the near-term, circulating SARS-CoV-2 variants will be derived from 」N.1.
In immunologically naive animal and human sera, XBB.1.5 and 」N.1 are
antigenically distinct SARS-CoV-2 variants. In non-nalve animals and humans,
post-monovalent XBB.1.5 vaccination sera, with or without recent prior infection,
neutralize XBB.1.5 and its derivatives including EG.5, HK.3, HV.1, as well as BA.2.86
and」N.1. However, neutralization titres against」N.1 in published and unpublished
studies were typically lower (2-5-fold) than those against the homologous XBB.1.5
immunizing antigen. There are further reductions in cross neutralization of 」N.1
variants with F456L and/or R346T substitutions.
Secondary analysis of published immunogenicity data demonstrates that an
additional vaccine dose with an updated vaccine antigen results in an averade
40% increase in neutralizing antibDodies to that variant as cormpared to vaccines
with a previous vaccine antigen. Using statistical modeling, the predicted
additional effectiveness of a vaccine dose with an updated vaccine antigen may
be approximately 23-33% against severe disease aS COImDared to a DreVIOUS
vaccine antigen and 11-25% against symptomatic disease.
In a context of high infection- and vaccine-derived immunity in the population,
contemporary vaccine effectiveness (VE) estimates are mostly relative (rVE),
rather than absolute (comparing vaccinated to unvaccinated individuals), and
demonstrate the added protection of recent vaccination over and above pre-
exiStindg infection- and vaccine-derived immunity:
o Bivalent (index virus and BA.1- or BA.4/5) mRNA vaccines and a Beta-Dbased
protein vaccine continue to offer protection against severe disease durind
periods of XBB descendent lineage circulation. Protection against
important regions of the spike protein of SARS-CoV-2.
As of April 2024, nearly all (>94%) SARS-CoV-2 genetic seduences in Dublicly
available databases are derived from」N.1, and these variants continue to displace
existindg XBB lineage variants (e.q. EG.5). This displacement indicates greater
fitness of」N.1 derived variants as compared to other circulating SARS-CoV-2
variants in the human population.
Several 」N.1 derived variants (e.d.」N.1.13.1,」N.1.11.1, KP.2) have independently
evolved changes in the spike protein at epitopes involving amino acid residues
346 and/or 456. Substitutions at these amino acid residues have been identified in
previous SARS-CoV-2 variants (e.q. R346T in BQ.1 and XBB: F456L in EG.5 and
HK.3) and are within epitopes known to be targeted by neutralizing antibodies.
Given the displacement of XBB lineage variants by」N.1 derived variants, it is likely
that in the near-term, circulating SARS-CoV-2 variants will be derived from 」N.1.
In immunologically naive animal and human sera, XBB.1.5 and 」N.1 are
antigenically distinct SARS-CoV-2 variants. In non-nalve animals and humans,
post-monovalent XBB.1.5 vaccination sera, with or without recent prior infection,
neutralize XBB.1.5 and its derivatives including EG.5, HK.3, HV.1, as well as BA.2.86
and」N.1. However, neutralization titres against」N.1 in published and unpublished
studies were typically lower (2-5-fold) than those against the homologous XBB.1.5
immunizing antigen. There are further reductions in cross neutralization of 」N.1
variants with F456L and/or R346T substitutions.
Secondary analysis of published immunogenicity data demonstrates that an
additional vaccine dose with an updated vaccine antigen results in an averade
40% increase in neutralizing antibDodies to that variant as cormpared to vaccines
with a previous vaccine antigen. Using statistical modeling, the predicted
additional effectiveness of a vaccine dose with an updated vaccine antigen may
be approximately 23-33% against severe disease aS COImDared to a DreVIOUS
vaccine antigen and 11-25% against symptomatic disease.
In a context of high infection- and vaccine-derived immunity in the population,
contemporary vaccine effectiveness (VE) estimates are mostly relative (rVE),
rather than absolute (comparing vaccinated to unvaccinated individuals), and
demonstrate the added protection of recent vaccination over and above pre-
exiStindg infection- and vaccine-derived immunity:
o Bivalent (index virus and BA.1- or BA.4/5) mRNA vaccines and a Beta-Dbased
protein vaccine continue to offer protection against severe disease durind
periods of XBB descendent lineage circulation. Protection against