I don't think the data on efficacy is any good for either one of them. They both just vaccinated a bunch of people and gave placebo to others. Kept track of Covid infections in both groups. That isn't a strong data set by a long ways. When they "rush" these products to market they are far more concerned with safety than they are with efficacy. So far, both have proven to be very safe in the short term. Long term, as well as real efficacy remains to be seen with both. Pfizer doesn't exactly have the best record with safety.
My main concern with the Pfizer product is the handling of the vaccine. It is a very fragile product with stringent handling requirements. Those requirements are going to get broken at steps along the way. How many doses of the Pfizer vaccine are going to be rendered inactive because of the handling. This is one of the things that would make regular approval of this product difficult in a normal environment.
I'll try and address some of the concerns in this thread and some from Jmez above.
First off, how is it not a strong data set? Both vaccine studies were very large >30k, double-blinded, placebo-controlled studies, which is the GOLD standard. The primary endpoints were pre-specified. The efficacy of both vaccines were abundantly clear (both FDA advisory committees voted overwhelmingly to support the emergency use authorization). I can tell you this study was highly watched as for once, we all had a stake in the game.
You are correct about the concerns for the handling of the Pfizer vaccine, but this is also highly regulated. I'm not saying there won't be some temperature deviations and lots that are thrown out, but these won't be administered. If I was able to give experimental ebola drugs in Africa without a dependable power source that had to be kept below -50, I'm not too worried about the vaccine here.
Okay, to address of the other comments: 1) The mRNA in the vaccine is directed to make the spike protein from SARS-CoV2. While mutations have occurred in this spike protein, there is no indication that this will greatly impact the efficacy of the vaccine. The issue with the influenza virus is quite different, but suffice to say not a similar comparison here.
2) There are still many unknowns, but what we do know are what the common side effects are (injection-site soreness, malaise, chills, joint pain). Most of these occur after the booster shot (i.e., when the immune system has been primed). What we don't know are the incidence of serious rare adverse events, however we should be getting a better handle on this quit soon as hundreds of thousands are being exposed. I would bet that some of these (e.g. 1/50,000) will occur, but hopefully the benefit/risk will stay acceptable.
3) There have already been some cases of anaphylaxis reported. This does not surprise me at all, especially given the lipid nanoparticle (think tiny fat globule...olive oil in vinegar) that is used to deliver the mRNA into are cells. This vaccine in some degree does what the virus does and hijacks our cellular machinery to make the spike protein so our immune system can then recognize it.
I'm happy to answer any other questions if I can. In full disclosure I'm not an expert on infectious disease or vaccine development, but I do have expertise on mRNA and drug development.
