Large new study shows that HPV vaccination protects against cervical cancer

It has been well-documented that HPV vaccination protects against genital warts and precursors to cervical cancer. Now, a large Swedish study confirms that the vaccination also reduces the risk of cervical cancer by as much as 88% if girls are vaccinated before turning 17 years old.

Updated 17 December 2020

A large Swedish study shows that HPV vaccination considerably reduces girls’ risk of developing cervical cancer.

Researchers from Karolinska Instituttet and Lund University, among others, have compared the risk of developing invasive cervical cancer among girls and women who have received at least one HPV vaccination to the risk among girls and women who have received no HPV vaccination.

More than 1.5 million Swedish girls and women aged 10-30 years were included in the study and followed from 2006 to 2017. The study shows a much lower incidence of cervical cancer among vaccinated girls and women compared to unvaccinated, in all age groups. Remarkably, girls who are vaccinated before reaching the age of 17 years reduce their risk of developing cervical cancer by 88% compared with unvaccinated girls.

Also protects against cervical cancer

It has previously been established that HPV vaccination prevents genital warts and changes in the cells of the uterine cervix when a person is vaccinated at an early age. The new study confirms that this is also the case for cervical cancer.

The risk of cancer was decreased by 88% when vaccinating before 17 years of age, whereas vaccination before 20 years of age and between 20 and 30 years of age reduces the risk by 66% and 64%, respectively. Even though the level of protection decreases when vaccination is given later than at 17 years of age, the health effects of vaccinatign in women aged 17-30 years are still considerable.

Clear result despite short follow-up period

Normally it takes a chronic HPV vaccination up to 20 years to develop into cervical cancer. Therefore, the 11-year follow-up period of the study is relatively short. Despite this, the researchers have found significant protection from cervical cancer in the vaccinated compared with the unvaccinated girls and women.

In Sweden, vaccination of girls aged 13-17 years with a four-valent HPV vaccine was initiated in 2007, and this is the type of vaccine examined in the study. The four-valent vaccine protects against HPV types 6, 11, 16 and 18, whereof types 16 and 18 cause approx. 70% of cervical cancer cases recorded globally. The HPV vaccines in the Danish childhood vaccination programme since 2009 also protect against these two types of HPV.

Boys are vaccinated nearly as frequently as girls

In Denmark, boys and girls are offered two HPV vaccinations when they turn 12 years old. The share of HPV immunization programmes initiated for girls born from 2003 to 2007 has been in between 81% and 87% range (vaccinated from 2015 to 2019).

For boys, 2008 is the first complete birth cohort that will be included in the childhood vaccination programme. In this cohort, which turns 12 years old in 2020, 61% have received HPV1 and have therefore initiated an HPV immunisation programme, whereas 12% have concluded the programme (as per 8 November). Among girls, 65% of the same birth cohort have received HPV1, whereas 14% have concluded their immunisation programme.

That is, the vaccination coverage for girls and boys is almost on the same level for children born in 2008. The share of children born in 2008 who have concluded their immunization programme is low because a minimum of five months must pass between the first and second HPV vaccination. Therefore, not all children born in 2008 have concluded their immunisation programme yet.
“The vaccination coverage of children born in 2008 is very similar between the sexes, both when we focus on all of Denmark and on provinces. This suggests that the vaccination programme has been well received by boys and their parents since it was initiated last year,” notes Head of Section Palle Valentiner-Branth from SSI.

At statistik.ssi.dk, you will find up-to-date figures describing the vaccination coverage among girls, and efforts are being made to present the coverage among boys also. Figures are expected to increase for the youngest birth cohorts as some lag is normal in vaccination as well as in reporting of the vaccinations given, and also because many persons from birth year 2008 have not yet received their final HPV vaccination.

Read the Swedish study: Lei, J., et al., HPV Vaccination and the Risk of Invasive Cervical Cancer. N Engl J Med, 2020. 383(14).

Read more about HPV vaccination at ssi.dk.