So there’s been lots of discussion about annual boosters.. I wonder if those boosters will suck as bad as the original vaccine..
Unknown, and there is better opportunity to do some dose finding now which might manage adverse effects vs efficacy.
Looks like Pfizer gives 79% reduction in risk for Delta (B.1.617.2 India) infection vs 92% against Alpha (B.1.1.7 UK) and protection against hospitalization is halved from 99% to 96%.
So that is good individual coverage still against Delta (similar better than we think it might be for Gamma Brazil P1 and Beta SA B1351, but some people need higher protection. The primary individual beneficiaries for boosters is going to be the highest risk individuals: those with risk factors for severe illness (especially nursing home residents and workers) or with risk factors for poor vaccine response (immunocompromised).
For population protection (herd immunity) the drop in coverage with the variant is concerning because you have less Ve against a variant with a higher R0 (more contagious) so you need better vaccine uptake (or a higher Ve in the form of a booster). I am concerned with plateauing vaccination rates and the virtual elimination of masking/distancing rules vs the reduced efficacy against
Delta and its imminently becoming the dominant variant by prevalence.
Good guestion. One of the important unknowns is how long antibodies last. Early on it was thought to be possibly 3-6 weeks, then it was maybe several months. I had COVID last year and when I donate blood, they check for antibodies. Last donation, no antibodies.
tldr; We think that immunity is very long lived, at least a year, perhaps lifetime, although natural infection appears somewhat less protective than the mRNA vaccines, particularly against variants, if you had been infected with the original China Wuhan Wild Type. Remember that immunity is not solely based on antibodies and negative qualitative antibody tests absolutely do not rule out immunity for someone previously infected.
Longer Read: I wrote this up for a similar question on another forum...
In Feb/March when they were investigating thousands and thousands of suspected reinfection in SA. Dr. Swaminathan (WHO Chief) was announcing the worry and there was also super concerning serology data from the Novavax placebo arm indicating previous infection was not protective in SA. We had plenty of in vitro data showing lower neutralization rates... this was following the January SA case spikes and partial collapse of the SA heatlhcare system. A few colleagues had family practicing back home and the stories of catastrophic surges were heartbreaking.
The questions was whether N501Y variants with the Eek mutation (E484K) like Beta Brazil and Gamma SA were going to have concerning reinfection rates... I did a lite review! There are some interesting
case studies but no great epi data to give rates except the inferred data from the Novavax serology.
Some things I did find.... Manaus Brazil where high
seroprevalence in didn't stem the surge, but was this due to reinfection or better transmission in the (more fit than wild type) Beta P1 variant? This
preprint suggested 28% of cases were reinfections, and they accounted for the higher tranmission rates, but it was model based, so whatever, potential for weaksauce study in my book is strong. Was it the same thing in SA? And the same story appears in
Dhaka where they surged with the Gamma B1351 variant and they had high rates of previous infection with reports of reinfection.
This was an interesting read in Cell.
Cross neutralizing between variants across 4 waves in Japan showed the weakest final reactivity against the Gamma B1351 SA variant.
This
preprint shows great (96% relative reduction) protection at 13 months after infection against reinfection but suggests reduced anti-S for Gamma B1351.
Preprint Theory on
CD4/CD8 response "picking up the slack" with the Gamma B1351 variant in the face of reduced antispike activity from antibodies.
There are so many limitations. The lack of WGS availability... lack of validation of previous infection... limitation on knowing if previous infections were wild type or something else... surmising with time/location based inference based on previous prevalence rates. All that makes it hard to put an efficacy rate on previous infection against particular variant... but the vulnerability exists and MAYBE (likely?) it is higher for certain variants.
SINGLE DOSE FOR PREVIOUS INFECTIONS?
For those previously infected, it does really seem that a single dose of mRNA vaccine is all that is needed. The
idea is a popular one.
Few studies I read on this topic were
this one from the Lancet:
"Among previously uninfected, seronegative individuals, anti-S titres after one vaccine dose were comparable to peak anti-S titres in individuals with a previous natural infection who had not yet been vaccinated. Among those with a previous SARS-CoV-2 infection, vaccination increased anti-S titres more than 140-fold from peak pre-vaccine levels (figure). This increase appears to be at least one order of magnitude greater than reported after a conventional prime-boost vaccine strategy in previously uninfected individuals.3"
Nature Medince
"spike-specific IgG antibody levels and ACE2 antibody binding inhibition responses elicited by a single vaccine dose in individuals with prior SARS-CoV-2 infection (n = 35) were similar to those seen after two doses of vaccine in individuals without prior infection (n = 228)"
IJID article:
"One dose boosts NtAbs in previously infected more than two doses in uninfected HCWs."
And this preprint:
"A single dose of BNT162b2 mRNA vaccine up to 15 months after SARS-CoV-2 infection provides neutralizing titers exceeding two vaccine doses in previously uninfected individuals. "
I thought there was another one that did a reanalysis of some subgroups from another large dataset, but can't find it...
ah here it is in a NEJM letter.
This is a
preprint addressing in a limited way vaccination vs previous infection:
Their data shows that vaccines work very very well and previous infection is protective.
2139 infection in the unvaccinated uninfected group (n=22777 attack rate 9.4%)
15 infections in the vaccinated uninfected group (n=26882, attack rate 0.56%)
0 infection in the vaccinated previously infected group (n=1220)
0 infection in the UNvaccinated previously infected group (n=1359)
A safe conclusion is that while vaccine is in short supply, previous infection should offer sufficient protection. What was the prevalent variant in Ohio (study site) during their study period of Dec '20 through May '21?
Alpha B117 (UK) appears dominant by April. But Gamma B1351 (SA) and Beta P1 were not very prevalent and Delta India was not present.
arstechnica.com
apnews.com
