You may have heard of the HPV vaccine, which protects against the human papillomavirus (HPV) — the most common sexually transmitted infection. HPV is important because certain “high-risk” types can cause cervical cancer, as well as vaginal, vulvar, anal, penile, and throat cancers. You can read more about HPV from the Mayo Clinic and the Cleveland Clinic.
A large Cochrane systematic review and meta-analysis (2025) looked at data from 225 studies, including 132 million people worldwide. The researchers examined what happened after countries introduced HPV vaccination programs and whether vaccination was associated with benefits or adverse effects. They mainly focused on people vaccinated at age 16 or younger, since earlier vaccination is known to be most effective.
Key Outcomes the Researchers Studied
The review examined whether HPV vaccination changed the rates of:
- Cervical cancer (learn more from ACOG)
- High-grade precancerous cervical lesions, including:
- CIN2+ (moderate dysplasia or worse) — explained by ASCCP
- CIN3+ (severe dysplasia or carcinoma in situ)
- Anogenital warts — see Harvard Health
- Other HPV-related cancers
- Adverse events (safety concerns) potentially linked with the vaccine
Researchers also rated the quality and certainty of the evidence using international GRADE criteria.
What the Review Found
1. Cervical Cancer Risk Drops After HPV Vaccination
The review found that HPV vaccination likely reduces the risk of cervical cancer, with moderate-certainty evidence across 20 studies.
In long-term follow-up of vaccinated groups, the risk of cervical cancer was reduced by about 63% overall (risk ratio 0.37). The benefit was even stronger in people vaccinated at age 16 or younger, where the risk dropped by about 80% (risk ratio 0.20).
This supports what many major medical groups already recommend — including ACOG and Stanford Children’s Health — that vaccination works best when given before someone is exposed to HPV, usually in early adolescence.
2. HPV Vaccination Reduces High-Grade Precancer (CIN2+ and CIN3+)
High-grade cervical intraepithelial neoplasia — called CIN2+ or CIN3+ — is a precancerous change in cervical cells. These conditions are detected by Pap or HPV screening and can progress to cancer if untreated. Learn more from Cleveland Clinic.
The review showed:
- CIN3+ decreased significantly after vaccination
- CIN2+ also decreased, especially when vaccination occurred at or before age 16
This means the vaccine prevents not only cancer, but also stressful procedures, monitoring, and treatment for precancer.
3. Fewer Cases of Anogenital Warts
HPV vaccination also reduced the rates of anogenital warts, which are caused by low-risk HPV types. These warts aren’t cancer, but they can be painful, embarrassing, and require treatment.
Across 47 studies, vaccination programs were linked with lower wart rates in both females and males in the medium and long term.
4. Limited Evidence So Far for Some Other Cancers
For rarer HPV-related conditions — such as adenocarcinoma in situ or vulvar cancer — there is still limited long-term data. These cancers are less common, so more time and research are needed to measure trends reliably.
Safety: Does the HPV Vaccine Cause Serious Health Problems?
A major part of the review examined potential adverse events that are often discussed online, such as:
- Postural orthostatic tachycardia syndrome (POTS)
- Chronic fatigue syndrome / myalgic encephalomyelitis
- Paralysis
- Complex regional pain syndrome
- Premature ovarian failure
- Infertility
- Increased sexual activity
- Guillain-Barré syndrome
The review found that HPV vaccination was NOT associated with an increased risk of these conditions. There was low-certainty evidence suggesting it also may not increase the risk of Guillain-Barré syndrome.
This aligns with prior safety assessments by groups such as the CDC and the World Health Organization.
Why Timing Matters
A key takeaway is that earlier vaccination — typically at ages 9–12 — provides the strongest protection. This allows the immune system to build defenses before exposure to HPV, which usually occurs after the start of sexual activity.
Both boys and girls benefit. Vaccinating everyone helps reduce HPV circulation in the community — a concept called herd protection.
What This Means for You
The authors conclude that HPV vaccination clearly lowers the risk of cervical cancer and high-grade precancer, especially when given during early adolescence, and long-term safety data remain reassuring.
If you have questions about HPV vaccination, talk with your healthcare provider or gynecologist. You can also review guidance from:
Bottom Line
HPV vaccination is a powerful cancer-prevention tool. The best protection happens when vaccination occurs early, and current research shows no increased risk of the serious side effects most often mentioned on social media. If you or your child haven’t been vaccinated yet, it’s not too late — ask your clinician what schedule is right for you.
El Camino Women’s Medical Group offers the latest Minimally Invasive Solutions for gynecologic problems. Drs. Amy Teng, Erika Balassiano, Pooja Gupta, and Vivian Wan, all members of AAGL (American Association of Gynecologic Laparoscopy), are highly trained and experienced in the field of Minimally Invasive Gynecologic Surgery. Dr. Erika Balassiano has also completed a Minimally Invasive Gynecologic Surgery Fellowship under the supervision of world-renowned Dr. Camran Nezhat. Angel Wong, PA-C, is a physician assistant who sees patients for routine and lower-acuity care.
All of our physicians are El Camino Hospital doctors and operate and deliver at the Mountain View campus.
As part of El Camino Women’s Medical Group’s commitment to comprehensive care for women, we offer in-network mental health services with world-renowned psychiatrist Dr. Rania Awaad and experienced therapist Daniya Ahmed, LMFT. For women seeking to improve their health through a healthier diet, Mariam AlAgha, MS, is an excellent nutritionist with over a decade of success helping women achieve their health goals. Her services are also in network.
Serving Mountain View, Los Altos, Los Altos Hills, Atherton, Palo Alto, Redwood City, Burlingame, Saratoga, Cupertino, Sunnyvale, Los Gatos, Campbell, San Jose, Santa Clara, Silicon Valley, Milpitas, Fremont, South Bay, East Bay, and North Bay.