12 April 2021 More positive news on mRNA vaccines

Mon, 04/12/2021 - 19:35

Episode 129

Dear colleagues,

Let’s leave all the Astra-Zeneca tribulations and consider the news about the other vaccines.

Anaphylactic reactions

Ep 129-1 is a nice didactic review on potential mechanisms and management of allergic reactions to currently used vaccines. For the mRNA vaccines PEG and polysorbate 80 have been incriminated; for Astra-Zeneca and J§J it is mainly Tween 80. 

Ep 129-2 provides further very practical Tables and boxes with key information on how to prevent and manage severe allergic reactions.

Boost of infection-induced immunity

 

Ep 129-3 the paper by Ebinger (previously in medRxiv, now in Nature Medicine) showing that people with previous SARS-CoV-2 infection experience a strong booster after 1st Pfizer dose and also have more moderate side effects.  Tentative conclusion: … our data suggest that a single dose of the

Pfizer–BioNTech vaccine is sufficient for individuals with prior SARS-CoV-2 infection, not only when considering the response in anti-S antibody levels but also when examining results of an ACE2 inhibition assay indicating the potential neutralizing capability of elicited antibodies.

 

Ep 129-4 Similar observation made by Vickers et al, withy the suggestion that these subjects could be good donors for convalescent plasma therapy.  I would think that one needs to show that the plasma also neutralizes the new variants.  Otherwise, it might be safer to rely on very potent broad-neutralizing combinations of monoclonal antibodies. 

 

Antibodies in breast milk after Pfizer

 

Ep 124-5: Kelly et al in Am J Obs Gyn show that Pfizer vaccination of 5 lactating mothers results in strong increase of both IgG and IgA SARS-CoV-2 antibodies in breast milk.  Remarkably, while IgG remained stable, IgA levels clearly decreased on the longer run (sometimes already after 1 month).  Neutralization was not attempted.   Anyhow, this observation argues in favor of potential protection of newborns by breast milk of vaccinated mothers.

 

Protection against infection

 

Ep 129-6 Jones et al in Elife confirm earlier data from Israel, showing at least 4 fold decrease of asymptomatic SARS-CoV-2 infection, from 12 days after 1st Pfizer dose.

 

Ep 129-7: Seemingly contradictory findings on efficacy of Pfizer vaccine against South-African variant

  • A is on 100 % effectiveness against COVID illness in a 800 South-Africans
  • B is on relative increase of new infections with South-African variants in 400  Israeli, who received one or two doses of Pfizer.

Clearly, these are press releases on rather small numbers. They need to be thoroughly analyzed and properly reviewed.  But, anyhow, these results look much better than what has been published  about poor performance of Astra-Zeneca in South-Africa.

 

Potential role of T cells

 

Ep 129-8 Encouraging data on CD4 T cell responses after mRNA vaccination:

  • Broad Spike-specific responses, with some peptides recognized by several participants
  • Very limited impact of mutations by British and South-African variants
  • Some evidence of cross-reactivity with common NL63 CoV

However, just IFN-gamma ELISPOT =  no direct evidence of anti-viral inhibitory effect and limited evidence of polyfunctionality.  In any case the results may suggest that T cell responses elicited or enhanced by SARS-CoV-2 mRNA vaccines may be able to control SARS-CoV-2 variants and lead to cross-protection from some endemic coronaviruses.

 

The enigmatic Chinese vaccines

 

Ep 129-9: according to a journalist paper in Science, the Chinese inactivated CoronaVac  is about 50 % effective in preventing symptomatic infections in health care workers in Manaus, where at the time of the roll-out 75 % of infection were caused by the “Brazilian variant” P1.  How well it protects against any infection or against severe disease needs to be clarified.  The paper also recognizes that at present, there is no comparison with mRNA vaccines. 

 

My ongoing frustration: no matter how hard I look, I cannot find even preprints on this and other trials with the Chines or Indian inactivated vaccines