IVaccination against cancer – so far this has only been possible in very few cases. Because very few types of cancer are triggered by pathogens against which there is a defense vaccine. Cervical cancer is one of them. There is a vaccine against the HP virus that causes it. For a long time, however, it was disputed whether and how well this vaccination works.
A long-term study from Sweden shows on a large database that HPV vaccination prevents many cervical tumors in women. The extent of the protective effect therefore depends heavily on the age at which the vaccination is given: If the participants received it between the ages of 17 and 30, the risk of disease fell by a good half within eleven years, as did the team led by Jiayao Lei from the Stockholmer Karolinska Institute in the New England Journal of Medicine. If the vaccine was given before the age of 17, the risk of tumors fell by almost 90 percent.
HPV vaccination can prevent dangerous cancers
So far, large studies had only shown that vaccination can prevent precursors of cervical tumors. “We show for the first time at a population level that HPV vaccination not only protects against cell changes that are precursors to cervical cancer, but also against cervical cancer itself,” says lead author Lei in a statement from her institute.
“Now we have proof that the HPV vaccination also prevents life-threatening carcinomas,” emphasizes Michael Wojcinski from the Professional Association of Gynecologists (BVF), who was not involved in the work. The results can be transferred to Germany, says the gynecologist.
In Germany, around 4,400 women are diagnosed with a so-called cervical carcinoma every year. Around 1,500 patients die every year from the disease, which often begins early: such early-stage tumors are diagnosed in Germany, according to the Cancer Information Service (KID) at an average age of 35.
The majority of these carcinomas are caused by human papilloma viruses (HPV). More than 200 variants of these viruses are known: Some of them cause normal skin warts, around 40 mainly affect the genital area and anus and are mainly transmitted through sexual contact.
Vaccines work against different virus strains
Some HP viruses can cause cervical cancer – in particular the two high-risk variants HPV16 and 18, which are responsible for about 70 percent of these cancers.
However, other influences also contribute to such tumors: risk factors include smoking, long-term use of birth control pills, a weakened immune system and other pathogens such as viruses of the herpes simplex type 2 and chlamydia.
In Germany, pediatricians and gynecologists currently offer two HPV vaccinations: a dual vaccine against HPV 16 and 18 and a nine-fold vaccine that protects against seven other HPV types (6, 11, 31, 33, 45, 52 and 58 ) directs.
A quadruple vaccine against HPV types 16 and 18 as well as 6 and 11 was approved in Sweden in 2006. In order to clarify the protective effect of this vaccination, the researchers evaluated the data of around 1.7 million women in Sweden in the period from 2006 to 2017. Almost 528,000 participants, who were 10 to 30 years old at the start of the study, had received at least one of the usual two vaccinations, 83 percent of them before the age of 17.
Cancer risk reduced by more than 50 percent
In Sweden, women are offered screening for cervical cancer from the age of 23. At the same time, the Scandinavian country runs a cancer registry, which makes such large studies much easier: 19 of the vaccinated women developed cervical cancer during the study period, compared to 538 of the unvaccinated.
If the scientists took into account possible influencing factors such as diet, tobacco consumption, exercise or the risk of cancer in the family, vaccination between the ages of 17 and 30 reduced the risk of developing the disease by 53 percent. The risk was reduced by 88 percent in women who had previously been vaccinated.
The authors explain this clear difference with the fact that the vaccination has no therapeutic effect in the case of an HPV infection. Therefore, it makes the most sense before the first sexual intercourse. This is also emphasized by Nobila Ouédraogo from the Cancer Prevention Unit at the German Cancer Research Center (DKFZ) in Heidelberg: “The vaccination is optimal if it is given before the first sexual contact, since HP viruses are mainly transmitted through sexual contact.”
Cervical cancer develops over decades
Because it can take decades for a tumor to develop after an infection, the German gynecologist Wojcinski expects that the protective effect will be even more pronounced with longer observation periods. The DKFZ expert Ouédraogo also assumes this: “Cervical cancer usually develops over a period of ten to well over 20 years. The observation period of eleven years is in the lower range.” With a longer observation period, the researcher expects, not only the number of cases recorded would increase significantly, but also the strength of the protective effect.
But even so, the Swedish authors see the study results as clear evidence of the success of the vaccination: “Our data strongly suggest that HPV vaccinations for children and adolescents should be continued as part of national vaccination programs,” says study leader Pär Sparén.
According to the researchers, 124 countries and territories had implemented national HPV vaccination plans at the end of 2019. The Swedish researchers write that at vaccination rates of over 50 percent, herd immunity is already noticeable – i.e. that people who are not vaccinated themselves also benefit from it. In Sweden and Australia, according to Wojcinski, the vaccination rate is 70 to 80 percent of girls.
A certain herd immunity is already evident in Sweden with regard to genital warts, writes Lei’s team – but not yet with regard to cervical tumors themselves. Since these often only appear after decades, the current period for this is still too short.
In Germany, the Standing Vaccination Commission (Stiko) recommends HPV vaccination for people aged nine to 14, but preferably before their 18th birthday. In Germany, according to the DKFZ expert Ouédraogo, only 43 percent of girls under the age of 15 are currently fully vaccinated. “It’s a shortcoming,” he says. According to him, at least 70 percent would be desirable. “Then the frequency of HPV infections in the population would drop significantly.”
In addition, the researcher points to clear differences between the federal states: Mecklenburg-Western Pomerania and Brandenburg have relatively high vaccination rates in the age group up to 15 with around 61 and 56 percent. Baden-Württemberg and Bavaria bring up the rear with around 34 and just under 36 percent.
Hardly any side effects, no damage
Since 2018, vaccination has also been recommended for boys, who transmit the pathogen primarily sexually. HPV infections can also cause carcinomas in them, but rare types of tumors such as anal, penile, mouth and throat cancer are affected.
The study did not examine any side effects of the vaccination. The cancer information service called “redness, slight pain, swelling and similar consequences, as many people know from injections and vaccinations in general”. There could also be headaches, rarely nausea, dizziness, fever and exhaustion. “The vaccines are considered safe and well tolerated,” was the conclusion.
An analysis of more than 20 studies by the Cochrane Collaboration in 2018 found no evidence that the vaccination leads to serious side effects. Wojcinski confirms this: “Permanent damage has not been seen so far.”
This article was first published in October 2020.