This study looked at mixing and matching AZ and Pfizer. It found that side effects were similar for all the combinations. It found that AZ first then Pfizer was about the same as Pfizer+Pfizer in terms of antibodies; it found that AZ+Pfizer or Pfizer+Pfizer gave more antibodies than Pfizer first then AZ or AZ+AZ.
When it came to T-cells, AZ+AZ was still the worst, with Pfizer+Pfizer and AZ+Pfizer about the same and Pfizer+AZ the best.
This still is not a true efficacy result, just test tube results.
This article found that, among people who had recovered from COVID-19, those who were unvaccinated were 2.34 times more likely to get reinfected than those who were vaccinated.
This tweet thread says that J&J is 67% effective against hospitalization with Beta, and 71% effective against hospitalization with Delta.
This article is long and exhaustive, but is an interesting look at global vaccine supply chains.