August 26, 2024
By Dr Nicoletta Hay, paediatrician, Morningside Clinic, Johannesburg
Vaccination for human papillomavirus (HPV) is a relative newcomer to the immunisation landscape. It has been introduced in a time of easy access to information through social media and accordingly, conspiracy theories abound. This is a quick summary of the vaccine and, in particular, why it should be considered for children (both male and female) and some adults.
HPV is a sexually transmitted pathogen that can cause anogenital and oropharyngeal disease in both males and females. Persistent viral infection with high-risk HPV serotypes – variations of the virus – causes virtually all cancers of the cervix. Cervical cancer is a leading cause of cancer in women all over the world.
In the absence of vaccination, it is estimated that the majority of sexually active adults will catch HPV in their lifetime. Many people infected with HPV do not show symptoms and are thus unaware that they are transmitting the disease.
Vaccines have thus been developed to protect against the acquisition of HPV infection – and therefore the subsequent development of HPV-associated disease. HPV vaccination thus reduces the rates of cervical cancer, as well as the incidence of genital warts and other cancers.
Six different vaccines have been developed worldwide – each varying in the number of HPV serotypes against which it protects. Not all are available everywhere: in South Africa we have Gardasil 9, which protects against nine serotypes, and Cervarix, which protects against the two most important HPV serotypes.
Of importance is that these are prophylactic vaccines: they are designed to prevent initial HPV infection. Therapeutic vaccines designed to induce regression of existing HPV lesions are in development, but are not in clinical use yet. Hence the drive to vaccinate before sexual debut – and the HPV vaccine is thus given in children from nine years of age, and optimally before 14 years.
What is of interest to many, is that the vaccine has health benefits for men. HPV vaccination also protects against cancers that affect them. These include anal, oropharyngeal and penile cancers. And it protects against the development of anogenital warts which, although not dangerous, can cause physical and psychological issues.
In addition, in settings where there has been a high uptake of vaccine among females, there is evidence of herd immunity among males of similar ages, as evidenced by reduction in genital warts.
For adults, vaccination is not routinely recommended, but is made on an individual basis. The likelihood of prior exposure to HPV vaccine serotypes increases with age, and if already colonised, the vaccine will not help. However, in people with no prior or very limited sexual exposure, the vaccine is encouraged if they are deemed to have a future risk of exposure.
Dosing
Ideally, vaccines are administered on a two- or three-dose schedule, and are given a couple of months apart. If vaccinating at 15 years or older, three doses are generally given due to a lower immunologic response to HPV vaccination.
It can be safely administered at the same time as other age-appropriate vaccines, just at different anatomical sites.
If the follow-up dose is missed, the schedule can be resumed without starting from the beginning.
Side effects
All approved HPV vaccines have documented safety in large clinical trials, and extensive post-licensing data.
They use virus-like particles that mimic HPV but do not contain genetic material. It is not possible to catch HPV or transmit HPV from the vaccine.
Side effects are few. The most common complaint is pain at the injection site. Other, more general side effects can include dizziness, nausea, headache, fevers and, rarely, allergic reactions. The risk of an allergic reaction to the vaccine is very low – 0.1 per 100 000 doses administered.
Anaphylactic and allergic reactions are the only true contraindications to further doses. Of note is that there is no thimerosal in the vaccines. This is an old mercury derivative that used to be used as a preservative.
Finally, getting the HPV vaccine does not mean that women can skip cervical cancer screening in the future, as there are more than 100 HPV serotypes. However, with vaccination, the risk of developing cancer is vastly reduced.
Note: The content shared is medical information for your knowledge. For a professional opinion or advice, please consult a doctor.
