COVID-19 Vaccines: What We Know So Far!

- By Dr. Vipin M. Vashishtha, MD @vipintukur

The Global Scenario:

➡️ Ten different Covid-19 vaccines have shared their Phase III data.

2 based on mRNA,
4 on viral vector,
3 on inactivated
1 on protein subunit platform.

1/n
➡️After 4 months of their trials, now there is a definite gradient in their performance:

Highly efficacious: mRNA,
Moderate: Viral vector,
Low to Moderate: inactivated vaccines.

(based on Trial Data and Post-trial Population Data)

2/n
➡️Efficacy (Point estimates as per published/shared data):

Pfizer 95%
Moderna 94.1%
Sputnik-V 91.6%
Novavax 89.3%
AstraZeneca (AZ) 62-90%
Sinopharm’s (BBIBP-CorV) 79%
Covaxin 78%
JNJ 72%
CanSino’s 65.7%
Sinovac’s (CoronaVac) 50.4%

3/n
➡️Quality of evidence (Confidence):

> Highest (Real-world use, Effectiveness data & Publication of Efficacy trial):

Pfizer
AstraZeneca
Moderna

> Moderate (Real-world use, Publication of efficacy trial):

JNJ
Sputnik-V
Sinopharm
Novavax

(contd)

4/n
>Low-moderate (Real world data, no publication of efficacy trial):

CanSino
Sinovac
Covaxin

5/n
➡️Israel, Chile, Bahrain, US & UK are the 5 leading countries as far as the highest share of the fully vaccinated population is concerned.

➡️Sinovac’s CoronaVac vaccine fared poorly in Seychelles & Chile.

6/n
➡️Pfizer & AZ vaccines have shown real-world effectiveness & population level impact. Though some level of confounding effects of non-pharmaceutical interventions was also present.

➡️Most vaccines have the highest efficacy against severe disease & deaths.

7/n
➡️No vaccine is 100% efficacious against SARS-CoV-2 SARS-COV-2 transmission infection (NO STERILIZING IMMUNITY).

Except for Pfizer/Moderna vaccines, most vaccines have only modest efficacy against transmission.

8/n
➡️Breakthrough infections observed with almost all vaccines. Most mild & moderate, deaths are also seen in fully vaccinated (out of 5800 breakthrough cases with mRNA vaccines in the US, 7% hospitalized & 74 died)

9/n
➡️Most vaccines have comparatively lower efficacy in the elderly & comorbidities than in younger and healthy people.

➡️Most gene-based vaccines (mRNA & Viral vector) have high reactogenicity profile.

10/n
➡️Adenovirus vector-based vaccines (AZ & JNJ) have rare, serious adverse events called VITT (vaccine-induced immune thrombotic thrombocytopenia).

Incidence varies from 1 case in 40 000 to 1 in 100 000, but the BENEFITS FAR OUTWEIGH THE RISKS.

nejm.org/doi/full/10.10…

11/n
➡️Efficacy against variants:

>Most vaccines have only very modest reductions in efficacy against UK’s B117 & Brazil’s P1 variants.

>Most vaccines have lower efficacy against South Africa’s B1351 variant (containing E484K mutation).

12/n
> AZ vaccine has got only 10% efficacy against B 1.351.

>JNJ (57%) & Novavax (49%) had major reductions in efficacy trials.

>Sputnik-V, Pfizer & Moderna vaccines have reduced neutralization against B1.351.

13/n
> Pfizer vaccine has shown intact efficacy against B1.351 in Qatar in real-world evidence after 2 doses.

>Nevertheless, most leading vaccines are developing boosters with revised formulation to tackle the B1.351 variant.

14/n
➡️So far, natural infection-induced protection seems to be more lasting than vaccine-induced, particularly in the context of non-mRNA vaccines.

>Things are still evolving. This is an observation based on 6-7 months post the trial reports. Too early to conclude anything.

15/n
> Also, the response of the human immune system to the invading virus is not uniform. Many patients with a severe infection also fail to have a good amount of Memory B cells.

>Whereas, with vaccines - such uncertainty can be avoided.

16/n
➡️Only 4 vaccine candidates elicited several folds higher titers of neutralizing antibodies (NAbs) than natural infection (NAbs titers measured in human convalescent serum):

Pfizer
Moderna
Novavax
Sputnik-V.

However, natural immunity is much broader.

17/n
➡️We know that natural infection provides at least 8 months of protection.

>mRNA vaccines are found to provide protection at least for 6 months without any appreciable loss of efficacy.

>Vaccines like inactivated & AZ vaccine may provide a lesser duration of protection.

18/n
➡️Natural infection may provide resistance against immune evader variants also since there are immune responses against not only against S protein but against other antigens of the virus.

Further, the variants do not have changes in T-cell epitopes.

19/n
➡️Most vaccines elicit both humoral and T cell immunity.

> However, viral vector vaccine, particularly the AZ vaccine has got particularly good CD8 cell response which kills the virus-infected cell and ameliorates the severity of the disease.

20/n
➡️Those had natural infection can ideally wait for THREE MONTHS for their Covid vaccine shot. (minimum time to wait is at least 4-6 weeks)

➡️In previously infected individuals with anti-spike IgG positive individuals, only ONE DOSE of mRNA vaccine is sufficient.

21/n
➡️Though no official recommendation from the WHO, still pregnant women can have the vaccine at any stage of pregnancy. Strong data for 3rd trimester with mRNA vaccines.

> FIGO and FOGSI have recommended vaccination of Pregnant women (2nd, 3rd trimester).

22/n
> No known risk in giving COVID-19 vaccines to women who are breastfeeding.

>Women who are breastfeeding should be encouraged to continue breastfeeding after being vaccinated.

23/n
➡️No need to avoid becoming pregnant after having the vaccine.

➡️There is no evidence to suggest that COVID-19 vaccines will affect fertility.

24/n
➡️Several vaccines are now conducting trials in the Pediatric population.

Pfizer - 100% efficacy in 12-15 yrs old.
Moderna - Trials in 6mo to 12 yrs (inUS) & 5-11 yrs (in Canada).
JNJ 12-17 yrs.
Sinovac 3-11 yrs.
Novavax 12-17 yrs.
AZ has paused their trial in 6-17 yrs.

25/n
Thank you, Dr. Vipin Sir @vipintukur for this.

To those with more queries, join us on Twitter Spaces on Tuesday, 11 May, 8:30pm with @vipintukur Sir and @ProfSomashekhar Sir.

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More from @HaryaxPathak

30 Apr
Let's talk about Vaccines.

Still seeing a lot of confusion going around about the Mechanism of vaccines in use. I will attempt to explain it as simply as possible.

Please read, and share.

So, think of the SARS-CoV-2 virus as Ferrero Rocher. 😋😋

1/n
Let's see the structure of the virus first.

Spike Protein = Nutty spikes
Lipid Membrane = Outer Chocolate Layer
Nucleocapsid = Wafery Layer
RNA = Innermost Chocolate

That's putting it very simply for the purpose of understanding.

2/n
Let's see how the virus causes infection.

The virus enters through our respiratory tract. It needs to enter a cell to replicate. For that, it uses the SPIKE PROTEIN (nutty spikes).

Spike protein allows the virus to enter the cell and cause infection.

Sweet and simple.

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What a day!!!!

1:30 pm -Live on @BBCNews
4:30 pm - Live on @bbc5live
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instagram.com/tv/CONJpuxp_9U…
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In view of the rising #misinformation campaign, I'll attempt to debunk some of the most common and widespread myths surrounding #COVID19India.

Read.
Understand.
Share.
Educate others.

1/n
➡️PREVENTION MYTHS

MYTH:
Wearing masks will reduce O2 and cause CO2 poisoning.

FACT:
Masks DON'T affect the O2-CO2 gas exchange at all. Masks won't reduce the oxygen or increase CO2 in your blood.

A study was also done to prove it. - atsjournals.org/doi/10.1513/An…

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2/n
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#Lemon juice through the nose will kill the virus.

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Dr. Haryax Pathak
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Admitted to hospital with severe symptoms.
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Even the groom's parents ended up positive.

Some got admitted in hospitals, some got home isolation.

Don't know about the situation with the bride's family and relatives.
Read 9 tweets

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