How effective is HPV vaccine? Are there any side effects?

The HPV vaccine is most effective in women who have never been exposed to HPV types 16 and 18 infections. Current data showed that it is 100% effective in preventing precancerous changes (CIN) caused by HPV types 16 and 18. However, HPV 16 and 18 infections account for 70% of cervical cancer. Therefore, vaccinated women can still be infected or have CIN caused by other HPV types.

As the vaccines cannot protect against infection by other high risk types of HPV, nor can they clear the virus in those who are already infected, they cannot eliminate the need of cervical screening. The HPV vaccine is generally safe. The common side effects are similar to that from other vaccines, such as soreness and swelling at the injection site, fever and headache. It should be avoided in pregnancy until more data on the safety in pregnancy are available. HPV vaccine is also not recommended for those who have ever had allergic reaction to any component of HPV vaccine.