If this source is legit — and I’ve never heard of it, so who knows — the headline is missing a pretty significant word:
> A fourth COVID-19 booster mRNA vaccine has proven ineffective against Omicron infection
> A fourth COVID-19 booster mRNA vaccine has proven ineffective against Omicron infection
Handy tip: When the article provides its source material and even links to it, it doesn't really matter whether you heard of it before or not.
On top of that: "Meanwhile, the European Medicines Agency (EMA) cautioned last week that there was no evidence to back a fourth booster, warning that repeat boosters every four months might actually weaken people’s immune systems". The source for that is also linked in the article.