HPV Vaccine Safety and Effectiveness Data

Data from Clinical Trials

Since late 2016, Gardasil 9 has been the only HPV vaccine available for use in the United States.

Each of the HPV vaccines that were once available —9-valent HPV vaccine (Gardasil® 9), quadrivalent HPV vaccine (Gardasil®), and bivalent HPV vaccine (Cervarix®)—went through years of strict safety testing before the U.S. Food and Drug Administration (FDA) licensed it. Each vaccine was found to be safe and effective in clinical trials.

• Gardasil 9 was studied in clinical trials with more than 15,000 females and males.

• Gardasil was studied in clinical trials with more than 29,000 females and males.

• Cervarix was studied in clinical trials with more than 30,000 females.

Vaccine Safety Monitoring Data

With more than 135 million doses of HPV vaccines distributed in the United States, there are robust data showing that HPV vaccines are safe.

• The most common side effects reported through CDC’s Vaccine Adverse Event Reporting System (VAERS) are pain, redness, or swelling in the arm where the vaccine was given, dizziness, syncope (fainting), nausea, and headache.

• With the exception of syncope, which is more common among adolescents after receiving any vaccine, there have been no confirmed adverse events occurring at higher than expected rates following HPV vaccination.

• On very rare occasions, a person may have a serious allergic reaction (anaphylaxis) to any vaccine, including HPV vaccines. In the United States, anaphylaxis following vaccination has a reported rate of 3 cases per 1 million doses administered. People with severe allergies to any component of a vaccine should not receive that vaccine.

Vaccine Safety Monitoring in the United States

The United States monitors safety of all vaccines through several systems:

• Vaccine Adverse Events Reporting System (VAERS) is a spontaneous reporting system that serves as an early warning system to detect possible safety problems that may be related to vaccination. Anyone can submit a report to VAERS. However, it is generally not possible to find out from VAERS data if a vaccine caused the adverse event, and the reports often lack details and sometimes contain errors.

• Vaccine Safety Datalink (VSD) is a collaborative project between CDC and eight healthcare organizations that monitors the safety of vaccines and conducts rigorous vaccine safety assessments.

• Clinical Immunization Safety Assessment Project (CISA) conducts vaccine safety clinical research and assesses complex clinical adverse events following vaccination.

Vaccine Effectiveness

Studies in the United States and other countries have shown that HPV vaccination is already preventing cancer-causing infections, anogenital warts, and cervical precancers. Some data from other countries have found early evidence of a vaccine effectiveness against cervical cancer.

HPV Infections

• Monitoring HPV vaccine prevalence is ongoing in the United States. As early as 4 years after Gardasil licensure, vaccine-type HPV infections had decreased 56% among 14–19-year-old females.(1)

• Within 12 years of vaccine introduction, infections with the four HPV types prevented by Gardasil decreased 88% among 14–19-year-old females and 81% among 20–24-year-old females in the United States.(2)

Anogenital Warts

• An analysis of healthcare claims data examined trends in anogenital warts among a large group of private health insurance enrollees in the United States. The study found that between 2006 (the first year HPV vaccination was recommended for females) and 2014, prevalence of anogenital warts among females decreased 61% among 15–19-year-olds and 44% among 20–24-year-olds.(3)

• Small declines in males in these age groups were observed starting after 2009. The initial decline in males was likely due to herd effects, as routine vaccination of boys was recommended in 2011.

Cervical Precancers

• Compared to 2008–2009, cervical precancer rates among screened females in 2014–2015 were 50% lower in 18–20-year-olds and 36% lower in 21–24-year-olds.(4)

• The percentage of cervical lesions due to HPV types prevented by HPV vaccination has dropped by 40% in vaccinated women since vaccines were introduced.(5)

Juvenile-Onset Recurrent Respiratory Papillomatosis

Juvenile-onset recurrent respiratory papillomatosis is a rare but serious disease caused by HPV acquired at birth. JORRP has declined significantly in the United States since vaccination was introduced in 2006.(6)

Studies from Other Countries

• Decreases in prevalence of vaccine-type HPV infections, anogenital warts, and cervical precancers have been observed in more than 14 countries with HPV vaccination programs, including Australia, Scotland, and others.(7)

• In Sweden and Denmark, women who had been vaccinated in their teens have been shown to have a lower risk of cervical cancer as adults.(8, 9)

Duration of Protection Studies

Data from clinical trials and ongoing research show that HPV vaccination provides long-lasting protection.

• Protection by HPV vaccination lasts for more than 10 years without becoming less effective.(10, 11, 12, 13)

• Studies are ongoing to further evaluate the duration of protection.

• No data indicate that the protection from HPV vaccination lessens over time.