Inge, I do not think it's possible to create a vaccine for a coronavirus that is not leaky. This was well-known in the scientific community prior to the pandemic, but the experts who dared to point this out were censored and silenced.

You might be interested in this article, which appeared in the early days of the pandemic. In addition to an inability to significantly prevent infection, the decades-old search for a coronavirus vaccine also yielded other unexpected problems:

"Studies have suggested that coronavirus vaccines carry the risk of what is known as vaccine enhancement, where instead of protecting against infection, the vaccine can actually make the disease worse when a vaccinated person is infected with the virus. The mechanism that causes that risk is not fully understood and is one of the stumbling blocks that has prevented the successful development of a coronavirus vaccine."

https://www.reuters.com/article/us-health-coronavirus-vaccines-insight-idUSKBN20Y1GZ