I've read that other countries are trying this too right now, Vaccine cocktail. Good step though, if it gets successful with higher efficacy then much better.
This virus has different variations, and so the data keeps changing too.
For example, they've increased the gap between Covishield doses, it was already done in other countries like Spain: 12-16 weeks, UK & Brazil: 12 weeks, Bangladesh: 8-12 weeks. They've to test country wise due to its having different variants.
And from now on the WHO will use Greek letters to refer to variants of COVID19.
Current variants of concern (VOC) are:-
Alpha - first identified in UK
Beta - first identified in South Africa
Gamma - first identified in Brazil
Delta - first identified in India
Source
Some updates regarding Vaccines:
Production which is going on right now of available vaccine ->

PS: The reason you're seeing other companies under Covaxin is because of this : "People say that Covaxin be given to other companies for manufacturing. I am happy to say that Covaxin manufacturing company (Bharat Biotech) has welcomed this when we discussed it with them. Under this vaccine live virus is inactivated & this is done only in BSL3 labs. Not every company has this. We give an open invitation to companies who want to do this. Companies that want to manufacture Covaxin, should do it together. Govt will assist so that capacity is increased: Dr VK Paul " Source
Some extra info - BIBOL produces Polio oral vaccine in India.
Bharat Biotech is working on Nasal Vaccine too.
Trial on age group 2-18yr is going on right now, they've received permission today. SII intends to begin clinical trial of the Novavax vaccine on children, soon.
Dr. Reddy's in talks to bring single-dose Sputnik vaccine into India, right now they are producing double dose Sputnik vaccine.
Vaccine by- Zydus Cadila, Biological E. and Gennova, are expected to come in market around June-August.
Novavax and BB Nasal ones around September.
Novavax global head delayed it, before it was announced by SII that it'll be launched by June. Experts have said that delay in raw material has caused this too and it was also reported that shortage of supplies like filters and single-use bags have also contributed to Novavax’s delay.
Zydus Cadila - DNA plasmid based vaccine
Gennova - mRNA based vaccine
Biological E. has tied up with Providence Therapeutics - mRNA based vaccine
J&J has tied up with Biological E. for its production too.
Zydus vaccine will be of 3-dose, can be stored at 2-8°C temperature. It is expected to be in market in June for adults only for now, they are working on children one too. They found out in Phase 1&2 trials that 3-dose worked much better, though they said that they are working on another 2-dose one too.
Pfizer wants indemnity protection against liabilities before they bring vaccines to India.
PS: Pfizer has sought indemnity and liability protection in its agreements with other countries too, which gives the firm legal protection from any claims linked to any adverse event after use of its Covid19 vaccine.
Moderna is in talks with Cipla, for manufacturing single dose vaccine in india. It'll come in 2022 (till now this info is available)

(Refer to Yahoo news link below for this list, this pic was taken during press conference)
Sources:-
https://www.livemint.com/news/india/pfizer-johnson-johnson-moderna-when-will-these-covid-vaccines-arrive-in-india-11622171764482.html
https://www.news18.com/news/india/zydus-cadila-working-to-get-nod-for-its-plasmid-dna-covid-vaccines-for-5-12-age-group-3791996.html
https://in.news.yahoo.com/india-moves-vaccinate-citizens-end-115155683.html
https://www.livemint.com/science/health/dr-reddy-s-in-talks-to-bring-single-dose-sputnik-vaccine-into-india-11622449642698.html
You can watch following interview (duration-34:05) DD news link :
https://m.youtube.com/watch?v=x4CkHYU-wms
https://www.financialexpress.com/lifestyle/health/trials-of-indias-first-mrna-covid-vaccine-by-gennova-on-track/2258977/
https://www.reuters.com/article/us-india-vaccine-idUKKBN2BJ0BI
https://www.wsj.com/articles/novavax-covid-19-vaccine-development-manufacturing-faces-delay-company-says-11620688615
https://www.cnbctv18.com/healthcare/explained-what-is-zycov-d-zydus-cadilas-homegrown-covid-19-vaccine-9298881.htm
https://www.hindustantimes.com/india-news/mumbais-haffkine-bio-pharma-to-manufacture-covaxin-centre-gives-nod-101618508212902.html
https://www.indiatvnews.com/news/india/bibcol-covaxin-production-bulandshahr-plant-bharat-biotech-covid19-vaccine-704133
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