>>13640436the main reasons why vaccines generally take longer to develop are:
1. The time it takes to raise funds
2. The time it takes to recruit trial participants
3. The time it takes for initial research
4. The time it takes for the government health authorities to prioritize reviewing and signing off on all the trial research
In terms of covid, number 1 and number 2 didn't take nearly as long given the $ stimulus from various governments and the drug companies, and the eagerness of volunteers to participate.
For number 3, Pfizer and Moderna were already doing a lot research on the mRNA vaccines, so had a good bit of the foundation laid (there have been phase 1 and 2 trials using mRNA vaccines for zika, rabies, HIV and the flu).
For number 4, most governments put reviewing the evidence at the top of the priority pile, and removed some bureaucracy (but not safety reviews!).
In terms of longitudinal studies, data dating back 50-60 years on new vaccines (polio, yellow fever, influenza) have demonstrated that most side effects occurr within 6 weeks of the vaccines being administered. This is why the FDA mandated for companies to provide a minimum of 8 weeks of data after the final dose.
