Thread by @SystemsVirology

BREAKING🔔 A new study from G2P-Japan🇯🇵 is out! The preprint will be out so soon, but we first show our results on the efficacy of XBB.1.5 monovalent vaccine - comparison between infection-naïve and XBB-infected individuals. Please retweet/repost🔥 1/

XBB.1.5 monovalent mRNA vaccine has been available since September 2023. However, we found that breakthrough infection with XBB subvariants, including XBB.1.5, does not efficiently induce humoral immunity against the infecting XBB subvariants. e.g., 2/

https://x.com/SystemsVirology/status/1701413583161266324?s=20

These observations raise the possibility that the XBB.1.5 monovalent vaccine may not be able to efficiently induce humoral immunity against emerging SARS-CoV-2 variants, including a variety of XBB subvariants as well as BA.2.86. 3/

To address this possibility, we collected two types of sera from individuals vaccinated with XBB.1.5 vaccine:
A) No prior infection
B) XBB subvariant infection prior to XBB.1.5 vaccination
We collected sera of pre- and post-vaccination and performed a neutralization assay. 4/

As expected, XBB.1.5 vaccine sera with prior XBB infection efficiently (1.8- to 3.6-fold) boosted antiviral humoral immunity against all variants tested. 5/

In the case of the XBB.1.5 vaccine sera without prior infection, XBB.1.5 vaccine also induced antiviral activity against all variants tested, suggesting a single dose of XBB.1.5 vaccine potentially induces antiviral immunity against XBB & BA.2.86 without prior infection. 6/

The induction efficiency of neutralizing activity was comparable between infection-naïve cohort (A) and XBB-infected cohort (B). However, in sera collected before XBB.1.5 vaccination, the neutralization titer of sera from (B) was 5.7- to 10.4-fold higher than that from (A)! 7/

Also, although all 'pre' vaccination sera of XBB-infected cohort exhibited antiviral activity against all variants tested, some 'post' vaccinated individuals without infection showed NO antiviral activity against XBB subvariants & BA.2.86 (# above 'Post' in A). 8/

Altogether, these results suggest that a single dose of XBB.1.5 monovalent vaccine may not be sufficient to induce effective antiviral humoral immunity in infection-naïve individuals and that a booster dose of XBB.1.5 monovalent vaccine may be required in some cases. 9/

Please also see fantastic results from Dr. David Ho's lab. 10/10

https://x.com/jbloom_lab/status/1729977752244338696?s=20

Preprint is out! Please find it as well👇

https://x.com/SystemsVirology/status/1730415196299231388?s=20