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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.
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- 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.
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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)
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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%
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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)
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>Low-moderate (Real world data, no publication of efficacy trial):
CanSino
Sinovac
Covaxin
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CanSino
Sinovac
Covaxin
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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.
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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.
https://www.nejm.org/doi/full/10.1056/NEJMe2106315
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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).
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> 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.
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>JNJ (57%) & Novavax (49%) had major reductions in efficacy trials.
>Sputnik-V, Pfizer & Moderna vaccines have reduced neutralization against B1.351.
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> 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.
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>Nevertheless, most leading vaccines are developing boosters with revised formulation to tackle the B1.351 variant.
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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.
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> 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.
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>Whereas, with vaccines - such uncertainty can be avoided.
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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.
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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.
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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.
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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.
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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).
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> 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.
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>Women who are breastfeeding should be encouraged to continue breastfeeding after being vaccinated.
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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.
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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.
To those with more queries, join us on Twitter Spaces on Tuesday, 11 May, 8:30pm with @vipintukur Sir and @ProfSomashekhar Sir.
