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Vaccines vs variants
A (not-yet-reviewed) study has been posted that looks at neutralizing titers for those with different vaccines against the variants of concern (VOC) (including Delta and Lambda).

Quote:SARS-CoV-2 variants have been classified by the World Health Organization (WHO)  based on increased transmissibility and/or pathogenicity as variants of concern (VOC;  Alpha (B.1.1.7), Beta (B.1.351), Gamma (B.1.1.248) and Delta (B.1.617.2) and variants of interest (VOI; Epsilon (B.1.427/B.1.429), Iota (B.1.526), and Delta plus (AY.1) and Lambda (C.37)
Quote:This study compared the neutralization titers of serum antibodies from individuals immunized with three U.S. FDA Emergency use authorization vaccines (BNT162b2 ["Pfizer"], mRNA-1273 ["Moderna"] and Ad26.COV2.S ["J&J"]) against viruses with the VOC and Lambda spike proteins.

If you download it, you may find it useful to skip to the Discussion section:

Quote:In sera collected
~3 months post-second immunization, BNT162b2 and mRNA-1273 mRNA vaccine-
elicited antibodies neutralized the variants with a modest 3-fold average decrease in titer
resulting in an average IC50 of about 1:600, a titer that is greater than that of convalescent
sera and likely, in combination with post-vaccination T- and B-cell memory responses, to
provide durable protection. Ad26.COV2.S vaccination-elicited neutralizing antibodies
showed a more pronounced decrease in neutralizing titer against the variants, raising the
potential for decreased protection against the VOCs and the Lambda variant. Vaccination
with Ad26.COV2.S resulted in IC50 titers against Beta, Delta, Delta plus and Lambda
variants that decreased 5-7-fold, resulting in mean neutralizing antibody titers of 33, 30,
41, and 36 against viruses with the Beta, Delta, Delta plus and Lambda variant spikes,
respectively, which according to mathematical modeling, could result in decreased
protection against infection . Modeling predicts that 50% protection from infection is
provided by a titer that is 20% that of the mean convalescent titer. In this study, given a
mean convalescent titer of 346 (Table S1), 50% protection would correspond to an IC50
of 69. The titer required to protect against severe disease was shown to be 3% that of the
mean titer of convalescent sera which in this study corresponds to a titer of 10. 

As I read that (I am neither a physician or one trained in this area), the Pfizer & Moderna vaccine series should provide much better than 50% protection against getting infected with the variants tested.  The J&J vaccine will provide less than 50% protection against getting infected, but will provide sufficient protection against getting severe disease.

To be responsible, I also point out that these results differ from some other studies for J&J.

Quote:The data reported here differ somewhat from those reported by Barouch et al. and
Jongeneelen et al. who found that Ad26.COV2.S-elicited antibody titers were mostly
maintained against the variants . In addition, Alter et al. reported a 5-fold decrease in
neutralizing antibody titer against Beta and 3.3-fold decrease against the Gamma variant
by the sera from Ad26.COV2.S vaccination which were less pronounced than those
reported here.

Finally, the authors reference studies that suggest a booster for J&J increase the neutralizing titers (thus providing better resistance to infection).
THanks for posting.  I"ll stay tuned for J&J booster when approved & recommended.

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