The evidence was not flimsy. Certainly not as flimsy as for Ivermectin.
VACCINES
https://www.nature.com/articles/s41467-022-31494-y
> Our results demonstrate that vaccinations reduce susceptibility to infection as well as infectiousness, which should be considered by policy makers when seeking to understand the public health impact of vaccination against transmission of SARS-CoV-2.
https://www.thelancet.com/journals/laninf/article/PIIS1473-3...
> The SAR [secondary attack rate] in household contacts exposed to the delta variant was 25% (95% CI 18–33) for fully vaccinated individuals compared with 38% (24–53) in unvaccinated individuals.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9807772/
> SAR was 35% and 23% for unvaccinated and vaccinated delta variant exposed contacts, respectively. SAR was 44% and 41% for unvaccinated and vaccinated omicron exposed contacts, respectively. Booster dose immunisation of contacts or vaccination of index cases reduced SAR of vaccinated omicron variant exposed contacts.
IVERMECTIN
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...
> For outpatients, there is currently low‐ to high‐certainty evidence that ivermectin has no beneficial effect for people with COVID‐19. Based on the very low‐certainty evidence for inpatients, we are still uncertain whether ivermectin prevents death or clinical worsening or increases serious adverse events, while there is low‐certainty evidence that it has no beneficial effect regarding clinical improvement, viral clearance and adverse events. No evidence is available on ivermectin to prevent SARS‐CoV‐2 infection.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9308124/
> The evidence suggests that ivermectin does not reduce mortality risk and the risk of mechanical ventilation requirement. Although we did not observe an increase in the risk of adverse effects, the evidence is very uncertain regarding this endpoint.