Common Cold and EBOLA and SARS are also in the class of Corona Virus. Attempts have been made to develop vaccines for these and have failed. Even those against the class of influenza are about 50% useless due to virus mutating.
Also, I read that intra-body cellular communication is done by similar transmission of pieces of RNA. So there is a potential for systemic injury by vaccine that creates antibodies against generic RNA pieces.
https://www.frontiersin.org/articles/10.3389/fmicb.2019.01781/full
MERS came out in 2012. This article is from 2019 (still no vaccine). On the other hand, death rates from MERS is down - so there are other factors at hand. Most probably because MERS is much more deadly than Covid-19, so the spread of MERS is less. Difficult to spread it when one dies so quickly of it.
But yeah - folks that believe a vaccine will help us are barking up the wrong tree.
Excerpt:
“Middle East respiratory syndrome (MERS) is a deadly viral respiratory disease caused by MERS-coronavirus (MERS-CoV) infection. To date, there is no specific treatment proven effective against this viral disease. In addition, no vaccine has been licensed to prevent MERS-CoV infection thus far. Therefore, our current review focuses on the most recent studies in search of an effective MERS vaccine.”