ndonesia to start phase III clinical trials of Sinovac COVID-19 vaccine on Tuesday
Vaccine is here! We are saved!
Unfortunately, not quite yet… This is another example of misrepresentation either by the news media or SinoVac themselves.
But lets us first define what Phase I, II and III trial do.
Phase I trial is to determine if the vaccine is safe for humans use. While all drugs, antibodies and vaccines are tested on animals, animal biology while similar is not identical. There are small difference that resulted in incidences where a compound found safe in test animals turned out quite unsafe in humans… we often find this in anticancer drugs. The duration of these trials is about 1 month to a year.
Phase II trial is to determine if the vaccine works to prevent SARS-COv2 infection and how long it is protective. This trial usually last 1 year and have a few hundred people in the trial
Phase III trial is to determine if there are any rare but serious side effects of the vaccine. Usually last at least 1 year, often more and has a few thousand people in the trial.
Sinovac like all other vaccine companies (Moderna/AstraZeneca) have decided, with approval of their host nations to implement a hybrid phase II/III trial. So unlike a regular phase III trial, we do not know if the vaccine works and for how long, even as large number of volunteers test out the new vaccine.
It is mentioned that briefly that Sinovac vaccine did induce antibody production (seroconversion) within a two week period, unfortunately potential short term immunity (since we do know if this immune response is sufficiently robust to fight off a SARS-Cov2 infection) is one thing, but a strong immune reaction 6 months to a year later is also another. I hope Sinovac vaccine performs better, because the other vaccines appear to start to lose potency within 2 weeks after the vaccine second boaster shot. Unfortunately Sinovac has not released any data about its vaccine. Nothing from its phase I safety trial and nothing to backup it antibody production claim. Furthermore Sinovac is still submitting Phase II trial protocol to China’s National Medical Products Administration, even as they start 'phase III' trials abroad.
So chances of immunization maybe not be 60% or 50%, it maybe 0%, because the vaccine fails to give immunity lasting more than 2 months. Or worse, actually caused the development of antibodies that coat the virus and improved its ability to infect cells, a phenomenon called Antibody-dependent enhancement (ADE). ADE has been observed in HIV, dengue virus, and coronavirus. Perhaps the most famous of ADE incident involved the 2017 dengue vaccine Dengvaxia, that has been since withdrawn by the Philippine government. This problem was detected after a 5 year phase III study of 20,000 children. I hope this will not be the case with Sinovac Covid19 vaccine or any other vaccines being developed, but we do not know.
I have also found mention that the Sinovac vaccine requires two doses. Thus reports that Indonesia will manufacture 200 million doses once the trial is complete, is insufficient for Indonesia 267 million citizens. That is only enough for 100 million people, a third of the population.
I want to make it clear to everyone, where exactly we stand. This trial in Indonesia and Brazil is really phase II trials, a trial to determine if the Sinovac vaccine works. There are potential complications with during vaccine development. This trial in Indonesia is expected to finish in half a year at the earliest, Feb 2021. It may take longer.