सिद्धार्थ Profile picture
May 24, 2021 17 tweets 8 min read Read on X
A short note on dosing regimen of COVISHIELD for complete vaccination.

We've 3 different set of trials:

1. UK/Brazil trials
This trial was open-label, w/ scandalous error in dosing regimen ("half-dose" error), had multiple major amendments in protocol when trial was undergoing Image
w/ minimum gap b/w 2 doses set to be 4 weeks.

COVISHIELD was initially supposed to be a single dose vaccine, but in middle of trial they realized that booster dose was required for higher efficacy compared to just single dose.

In the process, due to mfg/supply delay, intended Image
interval of 4 weeks was not achieved & got prolonged.

Attached are intended & extrapolated sub-group analysis that was carried out by PIs as part of protocol, w/ different dosing levels & intervals.

*extrapolated analyses were not part of protocol hypothesis but in response to ImageImage
the editors/referees.

Extrapolatory analysis can often be statistical gymnastics where you beat the data to extent that it gives inferences confirming your bias.

No one bought half & full dose combo despite it showing better efficacy since it was not part of actual hypothesis. ImageImage
The median interval between doses for the SD/SD group in COV002 was 69 days, i.e., 9.85 weeks (CI: 50–86, i.e, approx b/w 7 weeks to 12 weeks). Conversely, the majority of participants in COV003 in the SD/SD group (2493 (61·0%) of 4088) received a 2nd dose w/in 6 weeks of 1st. Image
Efficacy estimates from EMA, EU Commission for assessment of COVISHIELD was done with standard dosing regimen w/ 4 to 12 weeks as interval b/w 2 full doses.

2. India trial: This was bridging studies for safety & immunogenicity among Indian population
Image
and to compare equivalence of COVISHIELD w/ Vaxzevria.

Condition for regulatory authorization/approval is based on efficacy analysis from large RCTs abroad, while also taking consideration of safety signals from these trials.

Dosing schedule for Indian trial was two full doses
w/ interval of 4 weeks.

However, immunogenicity analysis was done at prematurely (against description of protocol). Even safety analysis have issues. Timeline & details of some important events regarding this are mentioned in thread attached.

ImageImage
3. US trial: Double-blind, large RCT w/ two standard doses at gap of fixed 4 weeks (28 days).

Trial results announced via press release was 76% efficacy against symptomatic COVID19 disease. It's more than efficacy from UK/Brazil trial for 2 std doses.

ImageImage
It's CRITICAL to note that proper verification on efficacy of a vaccine initially comes from a well-blinded sufficiently large-sized randomized control trials. Real-world data acts as supporting evidences.

Real-world data have limitations because there can be number of factors
that could have major role compared to vaccine in outcomes we see from real-world data. [RECOVERY trials are great example to know why RCTs are important than assertions based on real-world data].

Now we can turn around discussion to current dosing interval in India.
We have revised interval (gap) b/w 2 doses of COVISHIELD to 12 to 16 weeks based on extrapolatory sub-group analysis of UK/Brazil trial data, results published online on 8 December 2020 (last year).

Pics of recommendation from @WHO during Feb '21.
ImageImage
There's no proper real-world data from UK/India/EEA for dosing interval greater than 12 weeks (12-16 weeks) yet, because authorizations were w/ gap between 4 to 12 weeks in these nations. Only India extended the gap to 12 to 16 weeks, while UK reduced the gap to 4 to 8 weeks for
priority groups (50+ years and clinically vulnerable) amid real-world data showing concerning decrease in effectiveness against B.1.167.2 strains, 1st identified in India.

India will have to collect it's own real-world data for 12 to 16 weeks to perform
Image
statistical gymnastics.

COVID19 vaccines does provide some level of protection. What NTAGI COVID19 vaccine committee & NEGVAC should do is to prioritize two doses at interval of minimum 4 weeks for priority group (based on risk factor: age, clinical, occupation) so that they get
better protection than just from single dose (which seems to be too low against B.1.167.2 strains).

For non-vulnerable group w/ comparatively low risk factors, it would be better if all these vaccines are for now diverted to those w/ high risks.

NEGAV should consider
differential dosing intervals based on risk/vulnerability of group.

There needs to be complete transparency over assessment & rationale behind decisions. We cannot hype or underplay efficacy & safety factors of vaccines. Need balance w/ facts.

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More from @das_seed

Jul 2, 2021
Phase 3 trial results for COVAXIN (a double-blind, randomised, placebo-controlled trial). Thread.

medrxiv.org/content/10.110… 2 July 2021.

1. Vaccine efficacy against

● Symptomatic COVID19+ve: 77.8% (95% CI: 65.2–86.4) w/ 130 cases (24 COVAXIN, 106 placebo) Image
● Severe symptomatic COVID-19+ve: 93·4% (57·1–99·8) w/ 16 cases (1 COVAXIN, 15 placebo)

● Symptomatic COVID19+ve in age 18–59 yrs: 79·4% (66–88·2) w/ 109 cases (19 COVAXIN, 90 placebo)

● Asymptomatic COVID19+ve: 63·6% (29🤔–82·4) w/ 47(?) cases (13 COVAXIN+33 placebo=46🤦) ImageImage
2. Vaccine efficacy against symptomatic COVID19+ve

● B.1.617.2 (Delta): 65·2% (33·1–83·0) w/ 50 cases (13 COVAXIN, 37 placebo)

● B.1.617.1 (Kappa): 90·1% (30·4–99·8) w/ 11 cases (1 COVAXIN, 10 placebo)

3. Total 79 variants (VOIs or VOCs) detected in 130 cases analyzed for Image
Read 21 tweets
Jul 2, 2021
Based on recommendations from NTAGI, @MoHFW_INDIA on 2 July 2021 approved the vaccination of pregnant women against COVID-19.

Decision allows pregnant women to make an informed choice on taking COVID vaccination.

Decision communicated to the states/UTs.
pib.gov.in/PressReleasePa…
FAQ by @MoHFW_INDIA circulated among designated health practitioners before approval to allow COVID19 vaccination in pregnant women.

NTAGI had recommended studies to monitor safety of COVID19 vaccine in pregnant to be put in place immediately. Any update?
@MoHFW_INDIA says that pregnant woman opting for vaccination can get COVID19 vaccinated available in India any time during pregnancy.🤦‍♀️

(Not all vaccines have same safety profile. NTAGI had noted concerns along w/ recommendation to allow COVID19 vaccination for pregnant).
Read 6 tweets
Jul 2, 2021
Should Indians be concerned about commercial COVAXIN deals by @BharatBiotech?

@ICMRDELHI & @BharatBiotech have MoU on COVAXIN and also share Intellectual Property rights.

ICMR gets 5% on net sales of COVAXIN as royalty from BBIL.

Partial COVAXIN trials & mfg support from
Indian govt.

Not to forget super-extraordinary regulatory authorization to COVAXIN w/o Phase 3 trial data that allowed BBIL to opened door for early sales of COVAXIN in India & some other nations.

During early days, COVAXIN consignments only had BBIL's logo but not of ICMR.
However, there're COVAXIN consignments featuring logos of both developers, ICMR & BBIL, from March.

Commercial supply of 2 lakh COVAXIN doses to Mauritius on 19 March had logos of ICMR & BBIL w/ sign of #VaccineMaitri by Indian govt.

Was ICMR logo because of int'l shipment? No.
Read 8 tweets
Jul 1, 2021
What do we know about ZyCoV-D, a plasmid DNA vaccine candidate against symptomatic COVID19 by Zydus Cadila? Thread.

1. Results of pre-clinical studies on animals before July 2020 put in public domain in 2021:
biorxiv.org/content/10.110… 26 Jan 2021
biorxiv.org/content/10.110… 3 Feb 2021
2. Permission granted by DCGI on 2 Jun 2021 to initiate human trials adaptive Phases I & II.

Safety profile of 7 days after 1st dose of ZyCoV-D needed to be reviewed by DSMB & CDSCO before go ahead for Phase 2.

Some issues w/ these permissions are:
a) ZyCoV-D needs 3 doses for
completion (at day 0, day 28, day 56).

b) Vaccine candidate platform/tech is new for humans. 7 days for such a new vaccine candidate is too short period for monitoring. SAEs could occur based on dosages as well & some type of events may take longer to manifest.

c) Phase I trial
Read 26 tweets
Apr 11, 2021
A thread on recent updates (24 March- 9 April 2021) on Vaxzevria, a COVID19 vaccine mfg by AstraZeneca (called COVISHIELD if the same product is mfg by @SerumInstIndia).

1. Summary of productcharacteristics updated by @AstraZeneca after @EU_Commission's decision. Importantly, ImageImageImage
a) Thromobocytopenia is listed as common (≥1/100 to <1/10) adverse reaction

b) Thrombosis in combination w/ thrombocytopenia is listed as very rare (<1/10,000) adverse reaction

c) Currently available trial data do not allow an estimate of vaccine efficacy in 55+ yrs age group. Image
d) Asks healthcare professionals to be on alert for signs & symptoms of thromboembolism &/or thrombocytopenia. Instructs vaccinated people to seek immediate medical attention if they develop symptoms such as shortness of breath, chest pain, leg swelling, persistent abdominal pain ImageImage
Read 16 tweets
Mar 18, 2021
Pause of AZD1222 vaccine by some EU countries (Germany, Denmark, etc.) when UK has not raised any concerns, is relevant for India because > 85% of vaccine currently being admin in India is COVISHIELD (SII's AZD1222).

Thread on safety data from MHRA,UK

\1
Up to 28 Feb 2021:

1st doses of COVID19 vaccines administered by UK

- 10.7 million of BNT162b2

- 9.7 million of AZD1222

& ~ 0.8 million 2nd doses mostly of BNT162b2.

AEFIs reported via Yellow card:

- 94809 of BNT162b2

- 201622 of AZD1222

- 843 unspecified

\2 Image
Up to Feb 28, 2021 in UK:

~10.1 million received Pfizer/BioNTech's mRNA vaccine, whereas 9.7 million received AZ/Oxford vaccine

Deaths reported via Yellow card:

- 251* of BNT162b2

- 275* of AZD1222

- 6 unspecified

% of deaths in vaccine recipients: AZD1222 > BNT162b2

\3 ImageImageImage
Read 24 tweets

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