Fewer girls in Gainsborough and the rest of Lincolnshire are being vaccinated against the HPV virus that can cause cancer.
Girls across England are offered free HPV jabs during years eight and nine at school when they are aged between 12 and 14.
But Public Health England figures show that only 84.2 per cent of girls in Lincolnshire were given the recommended two doses of the vaccine in 2018/19.
This was a fall from 87.1 per cent the previous year, and meant 669 year-nine girls were left unprotected.
The HPV vaccination protects against the human papilloma virus, which is responsible for more than 99 per cent of cervical cancer cases, as well as some other more rare cancers.
According to the NHS, the jabs work best when girls receive it before they become sexually active.
HPV can be spread through any kind of skin-to-skin contact, as well as sexual intercourse.
The minimum vaccination target set by Public Health England is 80 per cent, but local areas are encouraged to aim for 90 per cent or above.
Across the country as a whole, the vaccination rate has declined from 86.7 per cent in 2013/14 to 83.9 per cent last year. However, it varied wildly from area to area, with London’s Waltham Forest as low as 56.7 per cent.
Robert Music, chief executive of cervical cancer charity, Jo’s Trust, said: “The jab is an extremely effective vaccine that will ultimatelysave lives. Yet many you ng women do not benefit. There is much targeted work to do.”