It stands to reason that * If the vaccine is safe and effective, life expectancy would improve some over 2020 * If the vaccine is safe and ineffective, life expectancy would stay about the same as 2020 * If the vaccine is unsafe and ineffective, life expectency would drop below 2020 We are now witnessing the third outcome.
So we need to carefully select individuals in both groups to be similar in there regards, or control for it statistically.
We will find out --some day soon-- if this vaccine was contributing to health or contributing to deaths. Given the fact that Pfizer wanted to hide the side-effects list from the public for 75 years I'm afraid it is the latter.