Sinovac, Sinopharm same technology welath ai me loku efficacy wenasak thiyenne?
@imhotep
They both are the same vaccine. The Chinese quotes these figures off from some trials done in the Middle-East areas. The Chinese Centre for Disease Control doesn't mention anything on efficacy, carefully omitting any reference to it other than the recommendations in administering the vaccine.
In fact, they list Pregnancy as a contra-indication and also specifically mentions that it's not necessary to delay a pregnancy
after vaccination.
The Indians call it the "Dud Vaccine" and say the efficacy claims have to be divided by two.

The Brazilian trial was done properly and the 50.4% figure was published by them.
All "inactivated vaccines" reported low efficacy rates from
any developer. Bharat BioTech claims they made refinements knowing the low efficacy and have succeeded, but they are on Phase III trials.
Another promising "Inactivated" candidate is the
French Valneva - still on the beginning of Phase III stage - they claim it's the only vaccine with the
whole virus, inactivated, adjuvanted. But no indication on efficacy as yet. They expect it to work on the variants. This only started last October 2020.
Sorry, I cannot give you a reason why these inactivated Covid vaccines are poor when compared with others. Nobody did studies on it and US scientists ditched that path completely in the initial stages of vaccine development. This was also partly because the trials with mice showed incomplete protection and also an undesired effect of eosinophilic pulmonary inflammatory response.
Currently everyone behind the DNA vaccine development and some are in early trial stage. None of these Generation 1 vaccines will work over the long term. It's either boosters or the DNA, the latter will take years for human use approval as only been used for veterinary use.