I have frequently heard variations of the following claim: "The vaccination reduces your chances of getting covid, and even if you do get it, it is much less likely to be severe." I can't find the source, but I recall a quote of someone saying that, if they tested positive after being vaccinated, they wouldn't be worried because the vaccine would reduce their chances of getting severe disease.
But, as I read the statistics, they seem to call this claim into question. Of course, different vaccines have different efficacies, but in general, the values seem to be in the same ballpark for the merely symptomatic and the severe categories.
I want to make two important points: First all the evidence indicates that the vaccines are very effective against all levels of severity. The statistics from Michigan below are hugely positive for the vaccine. There were less than three hundred cases out of 1.7 million vaccinated people, at a time when you would have expected many thousands if they weren't vaccinated. Being vaccinated makes the risk low enough that you can basically ignore it for most purposes. This question is about differences in effectiveness for more severe outcomes.
Second, the efficacy indicates how much the vaccine reduces a risk. So, if a vaccine has an efficacy of 95% against both documented infection and death, then it makes the chances of both 20 times smaller than they were, which is great.
All of that said, here are examples of what I mean:
- The Clalit study in Israel reports 92% efficacy for the Pfizer/BioNTech vaccine against both documented and severe infection. There were no deaths in the vaccinated group, but there were so few deaths in the control group that no real conclusions can be drawn.
- Another study in Israel found 92% efficacy against documented infection and approximately 97% efficacy against more serious outcomes. So, based on this study, the efficacy is almost the same against any symptomatic illness as it is against death.
- More informally, a report from Michigan indicates that there were 246 fully vaccinated residents who got covid, of whom 3 died. Both of these numbers are tiny compared to the vaccinated population, but of those rare people who did get sick, more than 1% died, similar to the general pattern. Also the accepted answer to this question suggests a roughly similar fatality rate for the country as a whole.
There are somewhat countervailing studies:
- The original Moderna study had no severe cases in the treatment group (but the number in the control group was only 30).
- Different sources report efficacy values for the Janssen/J&J vaccine of 60-75% for infection and values in the 80's for severe infection, a significant difference.
- This study from Qatar is maybe the most supportive of this idea. They find efficacies of 75-90% (depending on the variant) against documented infection, but 97.4% against severe disease.
Taking all the data together, can a fully vaccinated person with a symptomatic case of covid be reassured that their chances of death (given that they have a symptomatic case) are much less than if they had not been vaccinated? For instance, is there a strong argument for supporting the Qatar study over the Israel studies? Or are there reasons for thinking that the statistics on deaths among fully vaccinated people are misleading? (If most or all of the deaths are from cases that were acquired before full vaccination, that would be significant.)
I am also interested in the same question for severe illness as an outcome, which I should have made clear; this paragraph is being added in an edit.