The HPV vaccine protects against human papillomavirus (HPV), one of the main causes of cervical cancer. Vaccination reduces the risk of contracting the virus, but its positive effects appear to extend beyond that, according to Swedish research.
Pregnant women who had been vaccinated were at lower risk of several complications during pregnancy and childbirth, particularly premature birth.
These are very interesting results, says Cecilia Kärrberg, senior physician in gynecology and obstetrics at Sahlgrenska University Hospital in Gothenburg and one of the researchers behind the study.
HPV increases the risk
It has been known for some time that both HPV infection itself and treatment for serious cell changes in the cervix increase the risk of certain complications during pregnancy and childbirth.
We know that the more of the cervix is removed in women with serious cell changes, the greater the risk of premature birth, says Cecilia Kärrberg.
The study, published in the journal BMJ, shows that vaccinated women had about a 5 percent lower relative risk of premature birth than unvaccinated women.
"It's great to see that HPV vaccination can have positive effects beyond cancer protection. If we can reduce the proportion of premature births, it could have a major impact on public health," says Jiayao Lei, a researcher in medical epidemiology at Karolinska Institutet (medical university), who is also behind the study.
17 years ago
The associations were stronger among women vaccinated before age 17. Since 2012, all girls in grades five or six, and since 2020, all boys too, have been offered HPV vaccination.
"Now we have vaccination coverage of around 90 percent, and when those girls and young women become pregnant, the positive effect will be even clearer," says Jiayao Lei.
Because this is an observational study, it cannot establish that the vaccine causes the reduced risk, but the findings strengthen that hypothesis, according to the researchers.
The study, published in the journal BMJ, is based on Swedish registers and includes 624,713 deliveries of a single child to first-time mothers aged 16 to 35 between 2006 and 2023.
Of these women, 92,620 had received the quadrivalent HPV vaccine, which protects against four common HPV types, before pregnancy.
Vaccinated women had about a 5 percent lower relative risk of premature birth than unvaccinated women, and about a 15 percent lower risk of very premature birth.
Vaccinated women were also at lower risk of, among other things, premature rupture of membranes, stillbirth and neonatal mortality.
Among women vaccinated before age 17, the risk of developing cervical cancer is nearly 80 percent lower than among unvaccinated women.
Source: BMJ, Karolinska Institutet