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Monica Gandhi MD, MPH Profile picture
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2 Mar, 9 tweets, 4 min read
Two arms of the immune system- antibodies (from B cells) and T cells (two types, cytotoxic T cells or CD8+ and helper T cells or CD4+). Th1-CD4 cells and CD8 cells are the main immune defenses against viruses. Antibodies will rise & fall with time (depending on severity #covax1
Paper looked at SARS-CoV-2-specific CD4+ & CD8+ T cell responses from those who had natural infection with non-variant, compared to variants B.1.1.7, B.1.351, P.1, CAL.20C. Also looked at those vaccinated with Pfizer/Moderna against variants #covax1
biorxiv.org/content/10.110…
Several of these variants can affect antibody binding and function (either monoclonal or polyclonal), especially B.1.351 & P.1 (remember prevalence in J&J trial where severe disease outcomes unaffected). T cell responses affect disease severity, #covax1
sciencedirect.com/science/articl…
Want to ensure CD4 & CD8 T cell responses to SARS-CoV-2 remain intact, can still modulate disease severity if re-challenged with variant in future. Know CD4/CD8 T cell responses to natural infection showed breadth along multiple epitopes of virus, #covax1
sciencedirect.com/science/articl…
Same group in this paper looked at T cell responses after natural infection & after mRNA vaccination with variants. No difference seen between pool of spike protein peptides corresponding to ancestral sequence & those from variants - T cell reactivity to
biorxiv.org/content/10.110…
those pools remained intact if you had natural infection before or if you had mRNA vaccination (Pfizer/Moderna) before. What does this mean plain English? Prior infection or vaccination will provide robust T cell immunity to variants & re-exposure will be met with fierce T-cell
fight to ensure you do not get sick in future with variants (severe disease). Severe disease is what led us to know about SARS-CoV-2, otherwise this would have been another cold virus, gone unnoticed. This new paper is by comprehensive. #covax1. Variants will happen; proceed.
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More from @MonicaGandhi9

Monica Gandhi MD, MPH Profile picture
2 Mar
What are 3 immediate consequences of vaccines preventing asymptomatic infection (e.g. prevent forward transmission?): 1) vaccinated told they don't need to quarantine by CDC after exposure; 2) schools don't need distancing after teacher vax; 3) I would discourage surveillance
testing of asymptomatic individuals after vaccination with PCR tests. Why? Let's remember reason we do asymptomatic screening-to prevent transmission to others. A vaccinated person is safe from symptomatic infection so won't need routine screening for SARS-CoV-2 unless symptoms
Hope the data that, after vaccination- if you are exposed to SARS-CoV-2- the viral load in your nose will be low is convincing to you (two papers: medrxiv.org/content/10.110…
medrxiv.org/content/10.110…). If so, then you don't want to use a high sensitivity test like PCR for surveillance
Read 4 tweets
Monica Gandhi MD, MPH Profile picture
1 Mar
Let's put data on why vaccines reduce transmission all in 1 place: Beyond sheer biological plausibility that vaccine-mediated immune responses block viral replication in nose, through which you are most likely to spread the virus, as effectively as blocks elsewhere, data here:
Lancet preprint showed that health-care workers in UK swabbed every two weeks after vaccination had an 86% reduction in asymptomatic infection compared with unvaccinated individuals: papers.ssrn.com/sol3/papers.cf…
Other data in Lancet - health care workers vaccinated had 85% reduction in infection (asymptomatic & symptomatic) 15-28 days after 2nd dose
thelancet.com/journals/lance…
Read 8 tweets
Monica Gandhi MD, MPH Profile picture
28 Feb
UK today records lowest case in 5 months! I am sorry, the U.S. is not vaccinating fast enough. We are in a race of cases vs vaccines. UK had its own variant (B117) with likely increase in transmissibility & they could have lost their race but they didn't
independent.co.uk/news/health/co…
They didn't lose because they approved 3 vaccines- one adenovirus/DNA vaccine (AztraZeneca) + 2 mRNA vaccines (Pfizer/Moderna) & went crazy with roll-out: 1 dose to all first (2nd in 12 weeks). And remember, AztraZeneca is the one with less efficacy for mild disease with variants
but doesn't matter. Why? Because herd immunity means that you win race. You turn more sheep pink (two white not next to each other to pass) & virus slows down. We are not slowing our virus fast enough. We didn't approve a 3rd vaccine until today (J&J authorized today by the way)
Read 4 tweets
Monica Gandhi MD, MPH Profile picture
27 Feb
Great article! We keep seeing these amazing descriptions of the real-world effectiveness of vaccines. This one from 62,138 individuals from Mayo Clinics (Arizona, Florida, Minnesota, Wisconsin between 12/1/20-2/8/21. Compared 31,069 with (at least 1 dose)
medrxiv.org/content/10.110…
versus without vaccine propensity matched. 8,041 received two doses. Administration of two COVID-19 vaccine doses was 88.7% effective in preventing SARS-CoV-2 infection with onset at least 36 days after the first dose. Crazy. 88.7% similar to 94% in the trial.
And then here is a safety after vaccine data by same group as some offered vaccines want to wait for real-world safety data. Now remember, the adverse effects in clinical trials are "solicited" - people asked if they have injection site reactions
medrxiv.org/content/10.110…
Read 5 tweets
Monica Gandhi MD, MPH Profile picture
24 Feb
Here is full Johnson & Johnson dataset provided to FDA. Remember, this is one-dose vaccine and is an adenovirus vector with DNA inside your body will use to code for the full spike protein + receptor binding domain. We had press release data now have more
fda.gov/media/146217/d…
ENSEMBLE- Phase 3 randomized, double-blind, placebo-controlled trial of a single
dose (5x10^10 vp) of Ad26.COV2.S in ~40K participants
for pro-protocol analysis. Results 14 & 28 days after the one-dose (28 days likely best indicator given immunogenicity data that shows Ab titers
keep on going up in phase I/II data). Let’s start with worse outcomes & move backwards. . Deaths: 7 COVID-19 related deaths in placebo group and none in vaccine group so 100% protection against death. 29 hospitalizations in placebo group from COVID-19 and 2 in vaccine group so
Read 9 tweets
Monica Gandhi MD, MPH Profile picture
23 Feb
Some of this discussion after this article came out yesterday which shows that asymptomatic infection (transmission thereby) will reduce after vaccination reminded me how wed some are to continuing a narrative of fear. Remember how we used to say that "the clinical trials
designed to tell you if asymptomatic infection was reduced because post-vaccination regular asymptomatic screening was not done?" Well, here you have this done among HCWs after vaccination - swabbing just to make sure there is no virus in the nose & 86% of the time (these
are EXPOSED health care workers, they are around others), there was NO virus in that nose. Okay, what about the remaining 14%? Take these two papers please- tweeted details before so please read those.
medrxiv.org/content/10.110…
medrxiv.org/content/10.110…
Read 6 tweets

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