Vaccines and Cancer Prevention: Focus on HPV and Hepatitis B

by Neil Horowitz

How Do Vaccines Work?

Vaccines help protect us by training the immune system to fight specific germs before we ever encounter them. When you get a vaccine, it introduces a harmless piece or weakened form of a germ (called an antigen) into your body. This does not cause the disease, but it triggers your body’s defenses to react and learn:

1. Recognizing the Invader: The immune system sees the vaccine’s antigen and thinks it’s a real infection. It starts making antibodies (proteins that fight germs) and activates special blood cells to attack the antigen​pmc.ncbi.nlm.nih.gov.
2. Building Immune Memory: After the antigen is cleared, some of these defensive cells turn into memory cells. They stick around in your body for a long time​pmc.ncbi.nlm.nih.gov.
3. Quick Response Later: If the actual germ shows up in the future, the immune system remembers it. The memory cells quickly produce the right antibodies and attack the germ before it can make you seriously sick​pmc.ncbi.nlm.nih.gov.

In simple terms, a vaccine is like showing your immune system a “Wanted” poster of a bad germ. Later, if the real germ tries to invade, your body instantly recognizes it and fights it off. This prevents infection or illness from happening, or makes it much milder. By doing this, vaccines protect not just individuals but can also stop germs from spreading in the community (this is called herd immunity – when enough people are immune, the germ has trouble finding anyone to infect).

HPV Vaccine: Preventing Cervical, Anal, and Other Cancers

HPV stands for human papillomavirus, a very common virus. Most HPV types are harmless or cause warts, but some “high-risk” types can lead to cancer. In fact, HPV is the main cause of several kinds of cancer:

• Cervical cancer: HPV causes almost all cervical cancer cases​pubmed.ncbi.nlm.nih.gov. (The cervix is the lower part of the uterus, or womb.)
• Anal cancer: About 90% of anal cancers are linked to HPV infection​pmc.ncbi.nlm.nih.gov.
• Other cancers: HPV can also cause cancers of the vagina, vulva, penis, and throat (oropharynx)​pubmed.ncbi.nlm.nih.gov. This means if HPV infects those areas and doesn’t go away, it can make cells turn abnormal and eventually become cancer.

The HPV vaccine protects against the high-risk types of HPV that cause these cancers, especially HPV types 16 and 18 (the biggest cancer-causing strains)​

pubmed.ncbi.nlm.nih.gov. The vaccine is usually given in two shots to pre-teens (around 11–12 years old) before they are likely to be exposed to HPV. Here’s how the HPV vaccine helps prevent cancer:

• Stopping the Virus: The HPV vaccine is made of virus-like particles that look like HPV to your immune system (but contain no viral DNA, so they can’t cause infection). After vaccination, your body produces antibodies that specifically target HPV​pubmed.ncbi.nlm.nih.gov. Later, if you’re exposed to the real HPV, these antibodies can block the virus from infecting your cells.
• Preventing Cell Changes: By stopping HPV infection early, the vaccine prevents the virus from causing the cell damage or precancerous changes that it normally would. HPV-caused cancers usually develop years or decadesafter a persistent infection. With the vaccine, those infections don’t establish in the first place, so cells stay healthy.

Evidence of Effectiveness in Cancer Prevention (HPV)

Scientists have conducted many studies to see if the HPV vaccine actually lowers cancer rates – and it does. It’s important to note that cervical cancer can take a long time to develop, so researchers often first look at precancerous lesions (early cell changes that can turn into cancer) as well as actual cancer cases in vaccinated vs. unvaccinated groups:

• Fewer Precancers: Clinical trials found that young women who got the HPV vaccine had far fewer cervical precancer lesions. In one large review, the vaccine offered excellent protection against high-grade cervical cell changes (CIN2 and CIN3 lesions) caused by HPV-16/18 in women who were not already infected​pubmed.ncbi.nlm.nih.gov. This means the vaccine prevented the early warning signs of cervical cancer in those women. Similarly, vaccinated individuals had fewer precancer lesions in other HPV-related areas; for example, a study in young men showed about a 75% reduction in high-grade anal precancers among those who received the HPV vaccine compared to those who got a placebo​pubmed.ncbi.nlm.nih.gov. By preventing these precancers, the vaccine is expected to greatly reduce future cancers.
• Lower Infection Rates: After HPV vaccines became common, countries saw sharp drops in HPV infections. With fewer people carrying high-risk HPV strains, there’s less opportunity for these viruses to spread and cause cancers. This herd effect protects even those who aren’t vaccinated, but the biggest protection is in those who get the shots.
• Drop in Cervical Cancer Cases: Now that vaccination programs have been in place for over a decade, we have direct proof of cancer prevention. In England, for instance, girls began receiving the HPV vaccine in 2008. Researchers observed a dramatic decline in cervical cancer by the time these vaccinated girls grew into young adults. Among women who were offered the vaccine at ages 12–13, cervical cancer rates by their twenties were 87% lower than in unvaccinated women from earlier years​pubmed.ncbi.nlm.nih.gov. In other words, the vaccine almost eliminated cervical cancer in that young group. The protection was a bit less for those vaccinated at older ages (since some may have encountered HPV already), but still significant (34–62% reduction)​pubmed.ncbi.nlm.nih.gov.
• confirmation in Sweden: A large study in Sweden tracked 1.67 million women and found similar results. Overall, women who had the HPV vaccine had about a 63% lower risk of developing invasive cervical cancer compared to those who didn’t​pubmed.ncbi.nlm.nih.gov. Those who were vaccinated early (before age 17) had nearly an 88% lower risk of cervical cancer later on​pubmed.ncbi.nlm.nih.gov. This shows how crucial it is to vaccinate before exposure to HPV – early vaccination provided the strongest protection.

These findings are remarkable – they show that a vaccine can prevent a major cancer (cervical cancer) on a population level. Health experts predict that if high vaccination coverage is maintained, cervical cancer could eventually become very rare worldwide. There is ongoing research to see the vaccine’s impact on other HPV-linked cancers (like throat cancer), which take longer to show up, but since these cancers are often caused by the same HPV types, reductions are expected in the coming years as well.

Hepatitis B Vaccine: Preventing Liver Cancer

Hepatitis B is a virus that infects the liver. (The word “hepatitis” actually means liver inflammation.) Some people, especially if infected as babies or young children, can’t get rid of the virus completely – it stays in the body for a long time (this is called a chronic infection). Chronic hepatitis B infections can silently damage the liver over many years. The ongoing inflammation and liver cell damage can lead to cirrhosis (scarring of the liver) and increase the risk of hepatocellular carcinoma, the most common type of liver cancer​

pmc.ncbi.nlm.nih.gov. In fact, hepatitis B is one of the leading causes of liver cancer worldwide. Around one-third of liver cancer deaths across the globe are due to chronic hepatitis B infection​

pmc.ncbi.nlm.nih.gov, and in areas where the virus is very common, it accounts for up to two-thirds of liver cancer cases​

pmc.ncbi.nlm.nih.gov. The good news is that this cause of cancer is entirely preventable with a vaccine.

The hepatitis B vaccine protects you by teaching your immune system to block the hepatitis B virus (HBV). The vaccine is often given as a series of shots, starting with a first dose to newborn babies (since infants are at highest risk of becoming chronic carriers if infected). The vaccine contains a piece of the virus (a protein from HBV’s outer coat) that cannot cause infection but can trigger immunity. Once vaccinated, your immune system will attack the real hepatitis B virus if you’re exposed, preventing it from establishing a chronic infection.

Here’s how preventing hepatitis B infection leads to less cancer:

• No virus, no cancer: If the hepatitis B virus can’t infect you (because you have antibodies from the vaccine), it cannot cause the chain reaction of liver damage → cirrhosis → cancer. Essentially, the vaccine cuts the problem at the root by stopping the initial infection.
• Lifelong protection: The hepatitis B vaccine generates a strong immune memory. After the full course, most people are protected for many years, often for life. This means they are very unlikely to ever develop hepatitis B or its long-term consequences. If people aren’t chronically infected with HBV, their chance of getting liver cancer related to HBV is almost zero.

Evidence of Effectiveness in Cancer Prevention (Hepatitis B)

Hepatitis B vaccine was one of the first vaccines proven to prevent a major cancer. A striking example comes from Taiwan, which was one of the earliest countries to implement universal HBV vaccination. In 1984, Taiwan started giving hepatitis B vaccine to all newborns. Researchers then watched what happened to liver cancer rates in children over the following years:

• Sharp Decline in Childhood Liver Cancer: Before the vaccine program, liver cancer in children, though not common, was seen regularly in Taiwan (many cases were due to babies catching HBV from their mothers at birth and developing cancer by childhood). After the vaccination program began, the rates of childhood liver cancer plummeted. Studies found that the incidence of hepatocellular carcinoma in children ages 6–14 dropped significantly – from about 0.7 per 100,000 children in the early 1980s to 0.36 per 100,000 in the early 1990s​pubmed.ncbi.nlm.nih.gov. To put it simply, only about half as many children were getting liver cancer as a result of the vaccine program. For the youngest vaccinated kids (born just after the program started), the decrease was even greater: they had roughly one-quarter the liver cancer rate of children born before vaccinations​pubmed.ncbi.nlm.nih.gov. This was clear evidence that the vaccine was preventing cancer caused by the virus. Importantly, no other major changes occurred that would explain such a drop, so it was credited to immunization.
• Long-Term Protection: The benefit wasn’t just in small children. As the vaccinated children grew up, they remained much safer from liver cancer than past generations. A long-term follow-up study (looking at over 1,500 liver cancer patients in Taiwan) confirmed that those who received the hepatitis B vaccine as infants had much lower risks of developing liver cancer both in childhood and in young adulthood​pubmed.ncbi.nlm.nih.gov. This means the protection persisted as they aged. Essentially, an infant who gets immunized is far less likely to ever face hepatitis-B-related liver cancer even decades later.
• Global Impact: Many other countries have since adopted infant hepatitis B vaccination and seen similar positive trends. Globally, regions with high vaccine coverage have observed decreases in liver cancer rates attributable to HBV. For example, a large portion of liver cancers in parts of Asia and Africa (where HBV was once very common) are now being prevented thanks to immunization efforts​pmc.ncbi.nlm.nih.gov​pmc.ncbi.nlm.nih.gov. Health experts consider the hepatitis B vaccine a cornerstone of liver cancer prevention​pmc.ncbi.nlm.nih.gov​pmc.ncbi.nlm.nih.gov. It’s a powerful demonstration that stopping a virus can stop cancer.

Key Takeaways

• Vaccines “teach” the immune system to recognize and fight germs without causing the disease. They build an immune memory so your body can respond quickly if exposed to the real infection​pmc.ncbi.nlm.nih.gov. This prevents illnesses and their complications.
• Certain cancers are caused by infections. HPV (human papillomavirus) causes almost all cervical cancers and most anal cancers, among others​pubmed.ncbi.nlm.nih.gov​pmc.ncbi.nlm.nih.gov. Hepatitis B virus causes a large share of liver cancers worldwide​pmc.ncbi.nlm.nih.gov. By vaccinating against these viruses, we can greatly reduce the risk of those cancers.
• HPV vaccines protect against the HPV types most likely to cause cancer. They are most effective when given before HPV exposure (in pre-teens). Studies show HPV vaccination leads to far fewer cervical pre-cancers and up to 87–88% fewer cervical cancer cases in young women who were vaccinated​pubmed.ncbi.nlm.nih.gov​pubmed.ncbi.nlm.nih.gov. The vaccine also helps prevent other HPV-linked cancers (like anal cancer) by preventing the initial infection that would have led to cancerous changes.
• Hepatitis B vaccines are typically given in infancy to prevent HBV infection for life. This has a proven impact on cancer prevention: countries that vaccinate all babies have seen dramatic drops in liver cancer rates later on​pubmed.ncbi.nlm.nih.gov​pubmed.ncbi.nlm.nih.gov. Essentially, if people don’t get chronic hepatitis B, they avoid the main cause of liver cancer.
• Both HPV and hepatitis B vaccines have been validated in peer-reviewed scientific studies as effective tools for cancer prevention. They are safe and have additional benefits (HPV vaccine also prevents genital warts, and HBV vaccine prevents deadly liver disease beyond cancer). By using these vaccines, society can save thousands of lives each year and spare people the burden of cancers that we now know how to prevent.

Conclusion

In summary, vaccines can prevent certain cancers by stopping the infections that cause them. The HPV vaccine and hepatitis B vaccine are prime examples where immunization translates into cancer prevention. By getting vaccinated (and vaccinating our children), we arm the body’s defenses against these cancer-causing viruses. This means fewer infections, fewer cases of cancer, and healthier lives. It’s a powerful reminder that an ounce of prevention is worth a pound of cure – a few shots early on can lead to a lifetime of protection against some of the world’s most feared diseases.