When it first came out, I remember the controversies surrounding the HPV vaccine. Why vaccinate girls at such a young age? What are the long term effects? How long will immunity last? Almost a decade later, we are still exploring these and other questions. In the latest article on long term effects of the HPV vaccine, a group led by Dr. Benjamin Dorton of Brigham and Women’s Hospital at Harvard Medical School, has good news to report.
The HPV vaccine protects against the types of HPV that most commonly cause cervical cancer. These can include HPV 16, 18, 6, and/or 11. Prior research has shown that the vaccine is great at preventing pre-cancerous lesions and cancerous lesions. Older studies have already demonstrated that the vaccine works for women with no previous HPV exposure and for those who were exposed to the virus before getting vaccinated. Now these researchers are following up on these prior results, using real world clinical data to test out if all the prior findings hold up.
The good news is: they do! The researchers collected 1,392 patient records from women who had received abnormal pap smear results. This is important- the study sample did not include all women, but only those unlucky enough to already have some kind of abnormal finding. 481 or 34% of the women had received at least one dose of the HPV vaccine in the past. 911 or 66% of the women had not received the HPV vaccine.
After getting an abnormal pap smear result, these women went to their local “colposcopy” clinic in Boston. During colposcopy, the gynecologist looks at the cervix under a microscope (called a colposcope) and takes samples of the cervix so the pathologists can examine the cells for pre-cancer or cancer. The pathologists do two types of analyses: cytology (looking at individual cells) and histology (looking at the tissue sample as a whole). The study authors then compared the cytology and histology results for women who had received the HPV vaccine versus those who had not received the HPV vaccine. They found that women who had received the HPV vaccine had 53% lower odds of having the worst results on cytology and 36% lower odds of having the worst results on histology. The authors controlled for possible confounding factors including race-ethnicity, language, number of pregnancies, gonorrhea, and smoking status, to make sure that differences in these factors were not accountable for differences between the two groups of women.
This is good news for women who have been vaccinated against HPV! Now there is a large study conducted with real-world clinical data that supports the argument that the HPV vaccine protects against the worst kinds of cervical abnormalities, pre-cancers, and cancers.