Human papilloma virus (HPV) vaccination

1. What is HPV vaccine used for?

  • HPV vaccination helps to prevent around 90% of cervical cancers and pre-malignant changes at cervix. In addition, it may also prevent diseases caused by certain types of HPVs such as genital warts and anal cancer.
  • There are currently 3 licensed HPV vaccines globally – bivalent (HPV Types-16, 18), quadrivalent (HPV Types-6,11, 16,18) and nonavalent (HPV Types-6, 11, 16, 18, 31, 33, 45, 52, 58).
  • HPV types 6 and 11 are associated with genital warts but not cervical cancer. HPV types 16,18, 31, 33, 45, 52, 58 are ‘high-risk’ HPVs for cervical cancer and pre-malignant cervical changes, among which HPVs 16 and 18 are of significant risks and account for ~70% of all cervical cancer.

2. Who will benefit from HPV vaccination?

The Advisory Committee on Immunization Practices (ACIP) in USA recommends HPV vaccination for the following age groups:

  • Both males and females at 11-12 years of age (can start as early as 9 years old);
  • Adolescents and adults aged 13 to 26 years who have not been previously vaccinated or who have not completed the vaccine series. It is termed ‘catch-up vaccination’;
  • Individuals aged 27-45 years – decision based their risk of new HPV infection.

3. Does HPV vaccination have to be given before sexual activities begin?

Maximum protection can be obtained if vaccinated before becoming sexually active and exposed to HPVs. The vaccine does not treat any acquired HPV infection or cervical pre-malignant changes once they have occurred. However, having previous sexual activities does not preclude HPV vaccination. Despite sexual activities, few are infected with all types of HPVs and most may still benefit from the vaccination as they can get protection from the vaccine on unexposed types of HPVs.

4. Will HPV vaccination still offer benefit after abnormal cervical changes have happened?

For those with pre-malignant cervical changes (cervical intraepithelial neoplasia), HPV vaccination has been shown to offer benefit by increasing the chance of regression to normal and reducing the risk of recurrence of high-grade lesions following treatment. Therefore, even for women with CIN changes, HPV vaccination may still have values. Having said that, it is important to point out that the benefits of the vaccination are much greater prior to the HPV infection and CIN changes. Hence, one should aim to have the vaccination before these conditions have occurred.

5. Is the protection by HPV vaccination life-long? Is there a need for booster shots?

So far, there is no evidence of losing the protection against the vaccinated HPV types over time. Hence, the current belief is that there is no need for booster shots.

6. Can pregnant or breastfeeding women be vaccinated?

  • HPV vaccine is not recommended for pregnant women because of limited information about safety. Vaccination schedule should be postponed until the completion of pregnancy to finish any remaining HPV vaccine doses. On the other hand, inadvertent exposure of the HPV vaccination in early (unknown) pregnancy happens and so far, the available data have not identified any risks of fetal malformation or adverse perinatal outcome. Therefore, women with inadvertent exposure of the vaccine should be reassured and a termination of pregnancy is not recommended.
  •  Women who are breastfeeding can be vaccinated as the safety of breastfeeding is not affected. 

7. Who are not suitable for HPV vaccination?

  •  Anyone who has ever had allergic reaction to any component of HPV vaccine, including an allergy to yeast
  • Anyone who has ever had severe allergies to previous dose of HPV vaccine
  • People who are moderate/severely ill (i.e. having fever) 
  • Pregnant women

8. Immunization schedule and missed doses?

The ACIP and World Health Organization (WHO) recommend:

  • For adolescents aged 9-14, 2 doses of HPV vaccine (0 & 6-12 months later)
  •  For individuals aged above 15 years, 3 doses of HPV vaccine (0, 2 months and 6 months later), to be completed within 1 year
  • The minimum interval between the first two doses is four weeks, between the second and third doses is 12 weeks, and between the first and third dose is five months. 

If a vaccination schedule is interrupted for any length of time, the ACIP recommends resumption of the remaining dose(s) without restarting the series. Observational studies have not shown inferior immune responses following extended schedules.

9. Is HPV vaccination safe?

The safety of HPV vaccination is endorsed by international organizations, such as the Centers for Disease Control and Prevention (CDC) in USA and WHO. According to various clinical studies, most reported adverse events were mild and self-limiting, with pain at injection site, headache and fever being the most common ones.

10. After the HPV vaccination, is there any changes with the cervical smear screening programme?

The HPV vaccination cannot prevent all high-risk HPV infection and cervical cancer. Hence, even after completion of the HPV vaccination, routine cervical screening programme using the cervical cytology (pap test) with or without the high-risk HPV testing should still be practiced.


This article is contributed by Dr. T.N. Danny Leung
Updated on 30.12.2020