I suspect there is a high correlation between those who oppose mandatory bike helmet laws and antivaxxers.

On the contrary I fully support vaccines and I wear a helmet while cycling. The mandatory helmet law in Australia backfired pretty badly by reducing the numbers of people cycling. Those who promise mandatory laws for bicycle helmets tend to be anti-cycling and also tend to support notions that cyclists pay “road tax”.

The entire countries of the Netherlands, Denmark and China, to name a few, disprove your thesis.

Seen that you take a dig at anti-vaxxers... To be fair there's also a high correlation between the pro-vaxxers and those who believed the virus couldn't have possibly escaped from a lab.

Which was the official tune of the media, all synched, hammered for years. Now that tune has changed but that's another story.