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Vipin M. Vashishtha Profile picture
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7 Sep, 28 tweets, 11 min read
#Covid19 Vaccination: What do we have learned so far?

It is almost 9 months since the first Covid vaccine was injected to a UK national.

Let’s do a quick recap of the major ‘takeaways’ in next 25 tweets......................
1) Covid vaccines are highly effective against severe disease, hospitalization, & deaths in fully vaccinated individuals. Studies after studies from different countries in different continents with different vaccines have confirmed this fact

ndm.ox.ac.uk/files/coronavi…
2) Vaccines have only minimal impact on infection and transmission. They are not able to halt/prevent development of a new surge. The current Covid19 vaccines are effective in preventing symptomatic COVID19 disease but fail to prevent SARS-CoV-2 infection
nature.com/articles/s4159…
3) Different vaccines have different rates of effectiveness, particularly against Delta variant. Data so far suggests efficacy rates of approximately 67% for the J&J vaccine, 66-95% for the Moderna vaccine, & 42-96% for the Pfizer vaccine
healthline.com/health-news/he…
4) Despite rare serious side-effects, almost all vaccines are quite safe. Only few serious AEFIs vaccination have been found, all of them are rare, e.g. anaphylaxis, ViTT, vaccine induced thrombotic thrombocytopenia (VITT), myo-pericarditis, GB syndrome
cdc.gov/coronavirus/20…
5) There is a significant waning of vaccine effectiveness (VE) against infection and symptomatic disease. Waning more pronounced with mRNA than viral vector (AstraZeneca) vaccines

ndm.ox.ac.uk/files/coronavi…
6) Prior infection along w/ a dose of potent Covid vaccine offers the most robust protection against any VOC. A single dose of Covid vaccine is sufficient to provide high effectiveness against development of covid disease in previously infected individuals
nature.com/articles/d4158…
7) Waning may start as early as 2 months after the 2nd mRNA vaccine dose.

medrxiv.org/content/10.110…
8) It has not yet confirmed whether it is the TRUE waning or reduced effectiveness against Delta. The decline in effectiveness is not entirely surprising. Both the factors may be operational against the Delta variant

nejm.org/doi/full/10.10…
9- Vaccines may reduce the viral loads in vaccinated individuals; however, this reduction diminishes after 6 months. medrxiv.org/content/10.110…
10) Boosters are needed (after 6 mo) for protection against infection & symptomatic disease with most vaccines. #Israel has become the first country to roll-out booster vaccination campaign to offer a third dose of vaccine to people as young as age 50.

science.org/news/2021/08/g…
11) Dose of the mRNA may have a significant impact on NAbs production (Moderna (100 mcg)>Pfizer (30 mcg)>CureVac (12 mcg)). Among people previously uninfected, those who were inoculated w/ Moderna vaccine had 2.6 folds higher antibodies than Pfizer vaccine
journals.asm.org/doi/10.1128/Sp…
12) NAbs titers, not T-cells (CD4 & CD8) responses are the main ‘correlate of protection’ to evaluate covid vaccines. They are highly predictive of immune protection from symptomatic Covid disease. However, we still do not know the cut-off levels.
nature.com/articles/s4159…
13) NAbs are the mainstay of protection against infection than T cells responses. When it comes to long-lasting protection against COVID19, NAbs are our biggest allies. T cells may not be required for vaccine-mediated protection or ‘re-infection’.
science.org/doi/epdf/10.11…
14) Two-dose vaccines may NOT provide durable immunity. We may need 3-dose vaccine schedules for most vaccines. However, it is still not clear whether most people need them.

nature.com/articles/d4158…
15) Boosters do work: the reduction in viral loads after 6 mo of Covid vaccine is restored by the booster dose. Pfizer vaccine booster cuts infection risk by 70% or more in Israel. But the duration of protection even after booster is not yet certain!

fortune.com/2021/09/01/pfi…
16) We still do not know whether a ‘variant-specific’ booster will be more effective against or a booster with original strain against the outbreak propelled by a specific variant. No consensus whether a heterologous boost will give better results.
nature.com/articles/d4158…
17) Frequent boosting (extra doses) of Viral vector vaccines e.g., AstraZeneca is effective. Fear of interference with pre-existing vector-induced immunity was earlier considered a hindrance to extra doses of viral vector vaccines.

thelancet.com/action/showPdf…
18) Longer gap between two doses of mRNA & Viral vector vaccines improves immunogenicity & subsequent VE. New studies have shown that a longer interval between two doses of mRNA vaccines is also more efficacious.

jamanetwork.com/journals/jama/…
19) Mix-and-match of COVID vaccines trigger potent immune response. Results from several studies w/ different vaccines have shown the benefits of combining diff vaccines. However, we still don't have data on real-world efficacy & rare side effects

nature.com/articles/d4158…
20) Universal vaccination of healthy children is still debatable. Considering the very low risk of serious disease in 12-15 y w/out underlying health condition that puts them at increased risk.

gov.uk/government/pub…
21) Natural infection confers longer lasting and stronger protection against infection, symptomatic disease and hospitalization than vaccination. However, this does not mean natural infection is “preferable” to vaccination.

medrxiv.org/content/10.110…
22) Strategies based on achieving ‘herd immunity’ are redundant on the advent of new VOCs having significant ‘immune escape’ potential. Even without herd immunity, a transition toward normalcy is possible.

mckinsey.com/industries/hea…
23) No evidence of Antibodies-driven Disease Enhancement (#ADE) w/ current Covid vaccines. In fact, we see the opposite: those vaccinated are far less likely to become infected w/ SARS-2, & if they become infected, are far less likely to have severe dis
science.org/content/blog-p…
24) “Vaccine equity” has become the biggest JOKE of the pandemic. There are issues like ‘Vaccine Nationalism’ and hoarding of vaccines. The world today is 28% fully vaccinated: the richest countries 54% and the poorest ones a meagre 0.7%.

pandem-ic.com/new-estimates-…
25) #BOTTOMLINE: Vaccines are not silver bullets. We need non-pharmacological intervention (NPI) along with vaccines to take on Delta and other future VOCs.

ncbi.nlm.nih.gov/pmc/articles/P…
Addendum: Covid-19 vaccines are safe during pregnancy and breastfeeding. COVID vaccination is recommended for all people 12 years & older, including people who are pregnant, breastfeeding, trying to get pregnant now, or might become pregnant in the future

cdc.gov/coronavirus/20…
Here is my piece discussing some of these issues in details👇

@thewire_in
@TheWireScience
@1amnerd

science.thewire.in/health/nine-mo…

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More from @vipintukur

Vipin M. Vashishtha Profile picture
15 Aug
Will the newly identified sub-lineages of #Delta may initiate a new wave of #Covid19 in India? What impact the increasing prevalence of the Delta-D clade would have on global #COVID burden?

My write-up deliberating on these issues in @TheWireScience 👇 science.thewire.in/the-sciences/a…
#Delta variant and its extended family: How much do we need to worry?

During the first few months of the #pandemic, the evolution of the virus was relatively predictable, with substitutions accumulating at a fixed pace: 1 substitution every second week 2/
In contrast, the 2nd year of the #pandemic is punctuated by the emergence of several #variants that bore evidence of dramatic evolution 3/
Read 40 tweets
Vipin M. Vashishtha Profile picture
14 Aug
The #Delta is winning, for the moment, & the Global #coronavirus map shows that we’re failing to fight it. But the #pandemic will be over one day—but the way there is different now 1/
The virus will almost certainly be a permanent part of our lives, even as #vaccines blunt its ability to cause death and severe disease. Most people will meet the virus eventually; we must ensure that as many people as possible do so with two doses of vaccine in them 2/
The vaccines are working and working well. Vaccinated people are indisputably safer than unvaccinated people. But although vaccinated individuals are well protected, highly vaccinated communities can still be vulnerable, for 3 reasons: 3/
Read 20 tweets
Vipin M. Vashishtha Profile picture
13 Aug
The new #MayoClinic study finds Vaccine Effectiveness (VE) of #Pfizer shot dropped to 42% against #Delta #SARSCoV2 infection (not against hospitalization & deaths). 1/

medrxiv.org/content/10.110… Image
Earlier unpublished reports from #Israel also indicated the same 2/ ImageImage
Few other recent studies have also placed the #VE of Pfizer mRNA vaccine between 40-60% against #SARSCoV2 infection/symptomatic disease but not against severe disease & deaths. Table by @EricTopol 3/ Image
Read 7 tweets
Vipin M. Vashishtha Profile picture
6 Aug
How well are the current #Covid vaccines performing?

In all fairness, we can say they are offering high protection against severe disease & deaths; considerable protection against the symptomatic disease; but only modest protection ag. infections/transmission of the disease 1/
To put it another way, the vaccines are contributing little to our fight against the frequent surges of the #SARSCoV2 virus.

This leads to one pertinent question:

What ought to be the prime objective of the vaccination particularly amid an intense pandemic? 2/
To resist the ongoing outbreak or avoid hospitalizations and deaths?

A four-fold reduction in the hospitalisation & death rates is not much use if we just allow infections to reach four-fold the previous peak. 3/
Read 32 tweets
Vipin M. Vashishtha Profile picture
5 Aug
#Moderna says its vaccine shows durable 93% efficacy through 6 months.

Final analysis (median follow-up 5.3 mo):

-Against COVID19: 93.2%
-Against severe COVID19: 98.2%
-Against death: 100%

(Note: All data prior delta) 1/
Further break down of #Moderna efficacy by 2-month segments post 2nd dose; at month 4+, efficacy is 92.4%

#Pfizer vax (by months 4-6) efficacy is 84% - though against severe disease maintains 97%. 2/
Yet it expects antibody levels will start to wane, and with #delta there will be an increase in #breakthrough infections in fully vaccinated; it sees need for #boosters 3/
Read 8 tweets
Vipin M. Vashishtha Profile picture
12 Jul
For how long protection against reinfection with #SARSCoV2 lasts after a symptomatic #Covid19 disease? Almost FIVE YEARS, according to a new modelling study 1/
papers.ssrn.com/sol3/papers.cf…
The duration of immunity in #SARSCoV2 infected people remains unclear. Recent studies have estimated that the correlate of 50% protection from re-infection was 20% of the mean convalescent #NAbs titre 2/
The sera collected from a cohort of 125 individuals with RT-PCR confirmed SARSCoV2 infections up to 386 days after symptom onset. In the subset of 65 sera collected from day 151 to 386 after symptom onset, all remained positive in PRNT50 3/
Read 10 tweets

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