HPV Vaccine Effective, Vaccination Offers Herd Immunity [Study]
The HPV vaccine has been effective in lowering rates of human papillomavirus (HPV) after the vaccination was licensed for use in the United States in June of 2006, says a new study published in the August 2012 issue of the journal Pediatrics.
HPV is the most common sexually transmitted infection in the United States, with 50% percent of sexually active individuals becoming infected with the virus at some point in their lives. Most cases of HPV are asymptomatic, but some individuals will develop genital warts. Some strains of HPV are linked to an increased risk for cervical cancer as well as other, less common cancers including cancers of the vulva, vagina, penis, anus, tongue, tonsils, and throat.
In clinical trials, the HPV vaccine has been shown to be highly effective against the human papillomavirus. Widespread HPV vaccination has thus been recommended for women between 11 and 26 years of age as well as men through age 21. However, the impact of vaccination with the HPV vaccine on HPV prevalence rates in real-world, community settings was still uncertain.
Thus, for the present study, researchers at the Cincinnati Children’s Hospital Medical Center and the University of Cincinnati College of Medicine in Cincinnati, Ohio sought to compare the prevalence of HPV infection in young women before and after being vaccination with the HPV vaccine. The researchers aimed to determine whether rates of HPV decreased, whether the HPV vaccine provided herd immunity, and whether the HPV vaccine caused increased rates of nonvaccine-type HPV.
The current HPV vaccine protects against only certain strains of the HPV virus. Thus, researchers have been wondering whether individuals vaccinated with the HPV vaccine were at an increased risk for becoming infected with strains of the virus not included in the vaccine. Researchers have also been wondering whether the use of the HPV vaccine provides herd immunity against the strains included in the vaccination.
To determine the effectiveness of the HPV vaccine, the researchers looked at young women who were between 13 and 26 years of age during the years of 2006 and 2007 and who had been or who were sexually active. Rates of HPV infection were assessed before and after the women were vaccinated with the HPV vaccine.
After vaccination with the HPV vaccine occurred, the rates of infected with vaccinated-type HPV strains decreased from 31.7 percent to 13.4 percent. Thus the HPV vaccine was determined to be effective against the HPV virus.
The HPV vaccine also appears to offer herd immunity. Herd immunity occurs when the vaccination of a significant portion of the population provides a measure of protection for individuals who have not developed immunity. After vaccination with the HPV vaccine, the rates of infection decreased from 30.2 percent to 15.4 percent among individuals who had not received the vaccine.
However, nonvaccine-type HPV infections increased from 60.7 percent to 75.9 percent among the women who had received the HPV vaccine.
The results of this study indicate that the HPV vaccine is highly effective in lowering the rates of HPV infection among sexually-experienced young women. Additionally, the HPV vaccine offers herd immunity, further protecting individuals who have not yet been or who cannot be vaccinated against the virus. These findings indicate the importance of vaccination with the HPV vaccine for all teenagers and young adults.
As the researchers conclude:
“We found evidence of a substantial decrease in vaccine-type HPV prevalence in the community, as well as evidence of herd protection, only 4 years after the quadrivalent HPV vaccine was introduced; this is expected to translate into a decrease in CIN and ultimately cervical cancer in the community.”
Further research needs to be conducted on the increase in nonvaccine-type HPV in participants vaccinated with the HPV vaccine.
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