The study is linked early in the article and is fairly dense, the article summarized it well and is a lot more readable.

16/18 are the most carcinogenic strains, they have been close to eradicated in Denmark. "Denmark close to wiping out leading cancer-causing HPV strains after vaccine roll-out" is the full headline and 100% accurate.

Those were the only two high risk strains covered by the vaccine used in the time frame studied. The study covers the first cohort of girls given the 2008 version of the vaccine when they recently reached age to start screening. It is expected to not see other strains affected in this study, even though current vaccines are broader. The total number of high risk HPV cases in the study went down post-vaccination.

The notion of numbered strains of HPV is about diverging lineages going back hundreds of thousands of years in a highly conserved, slowly mutating virus. They are not comparable to things like seasonal COVID or flu strains.