For people who are members of Medscape (you can join for free) this is an interesting review of Novavax and another new vaccine, Covaxin.
https://www.medscape.com/viewarticle/975110
I think we are now at the stage that the main issues in vaccine appraisal will be the incidence of adverse events and the "breadth" of the antibody response. It does seem that in the future, mixing vaccines is the way to go rather than continually developing variant specific vaccines. Many, if not most, of the vaccines in development, that have been shown to be effective have been discontinued. For these vaccines to be economically viable they need to offer advantages beyond their effectiveness, the first vaccines set a very high bar.
It is still difficult to estimate the risks involved in vaccination, any sort of activation of the immune system may increase some risks and it seems to be the case that the immune response to some specific pathogens can be associated with some specific problems. However, the fact that interactions with our environment mean we are constantly exposed to a range of antigens means that there is usually a constant background rate of many of the suggested adverse events.
Only vaccines that can be associated with low rates of possible adverse events are widely used, in many cases it can be difficult to identify any increased rate as the frequency is so low it can be difficult to identify different rates of occurrence. This was an issue with the Astra Zenica / viral vector vaccines and is considered in the review of Novavax. Many of the adverse events identified are frequently seen in actual infections and at a much higher rate.
A great deal of attention is paid to the possibility of adverse events to vaccines, and the global monitoring systems mean that information about individual cases is widely available and influences uptake. This is a prime example of how human stories influence behaviour when good quality information doesn't. If we looked at measles vaccination about which we have detailed information over many years, its clear it is very safe, there are very few cases of serious side effects that can be attributed to the vaccine, and it provides lifelong protection. At the same time vaccine refusal, often in areas of high risk is very common, despite vaccination campaigns leading to an 80% reduction in deaths between 2000 and 2017, the WHO still reported around 110,000 deaths over this same period.
With Covid we saw widespread campaigns to ensure equal distribution of vaccine stocks to African countries and the development of vaccine production facilities. Unfortunately, and for a variety of reasons, despite the vaccines being made widely available, vaccine uptake remains very low, a new production facility in South Africa was in fact closed for lack of orders. I suspect that the idea that new vaccines that use different technologies will reassure people who were suspicious of mRNA vaccines and increase uptake, may be a triumph of hope over experience.