If you’ve heard of hepatitis, you probably know it has something to do with the liver. But there’s a whole family of hepatitis viruses, each with its own personality when it comes to how it spreads, what it does to your body, and how we can prevent or treat it. Let’s walk through the three most common types—hepatitis A, B, and C—and then dive into a controversy that’s making headlines right now: the hepatitis B vaccine.
What Is Hepatitis, Anyway?
At its core, hepatitis just means inflammation of the liver. Your liver is a workhorse organ that filters toxins, produces essential proteins like albumin, processes amino acids, and stores energy. When a hepatitis virus attacks it, the inflammation can range from a minor inconvenience to a life-threatening condition. The three main culprits—hepatitis A, B, and C viruses—are completely different organisms that just happen to target the same organ.
Hepatitis A: The Food and Water Troublemaker
Hepatitis A is often called “traveler’s hepatitis” because it spreads through food and water that are contaminated with fecal matter. Think of it as the virus you might pick up from eating unwashed produce, drinking contaminated water, or consuming raw shellfish from polluted waters. Other risk factors include unprotected sex and IV drug use. According to the CDC, there were an estimated 3,300 acute infections in 2023 in the United States.
The good news about hepatitis A is that it typically heals itself within 2 months. When symptoms appear—which take about 15 to 50 days after infection—they can include jaundice (that yellowing of the skin and eyes), fever, fatigue, nausea, and dark urine. Many young children don’t show any symptoms at all. The virus doesn’t become chronic, and once you’ve had it, your body produces antibodies that protect you for life.
Prevention is straightforward: there’s a safe and effective vaccine, and basic hygiene goes a long way. Wash your hands thoroughly, especially after using the bathroom and before preparing food. When traveling to areas with questionable water quality, stick to bottled or boiled water and avoid washing raw food in local water.
Treatment is mostly supportive—rest, fluids, and time. Your liver does the healing work itself.
Hepatitis B: The Blood and Body Fluid Virus
Hepatitis B is where things get more serious. This virus spreads through blood and other body fluids, which means it can be transmitted through sexual contact, sharing needles, or from mother to baby during childbirth. Healthcare workers are especially at risk from needle sticks and sharps injuries. It’s a highly infectious and tough virus that can live on surfaces for up to a week. Even tiny amounts of dried blood on seemingly innocent things like razors, nail clippers, or toothbrushes can potentially spread the infection.
According to the CDC, there were an estimated 14,400 acute infections in 2023, Approximately 640,000 adults were living with chronic hepatitis B during the 2017-2020 period and that’s what makes it particularly concerning: while the hepatitis B virus often causes short-term illness, it can become chronic.
The incubation period is long—typically 90 days with a range of 60 to 150 days. When symptoms do appear, they mirror hepatitis A: jaundice, fatigue, abdominal pain, nausea, and dark urine. But here’s the frightening part: most young children and many adults show no symptoms at all, meaning they can spread the virus without knowing they’re infected.
The chronic infection risk varies dramatically by age. If you’re infected as a newborn, you have a 90% chance of developing chronic hepatitis B. For adults, the risk drops to under 5%. Those with chronic infection face serious long-term consequences—15% to 25% of people with chronic infection develop serious liver disease, including cirrhosis, liver failure, or liver cancer.
Treatment for acute hepatitis B is supportive, but several antiviral medications are available for people with chronic infection. These don’t completely eradicate the disease but produce a “functional cure” that significantly slows liver damage and reduces complications.
Prevention is critical. There’s a highly effective vaccine—we’ll talk more about the controversy surrounding it in a moment. Avoiding exposure to infected blood and body fluids is essential. This means safe sex practices, never sharing needles or personal care items that might have blood on them, and ensuring proper sterilization of medical and tattooing equipment.
Hepatitis C: The Silent Epidemic
Hepatitis C is transmitted primarily through blood-to-blood contact. The most common route is sharing needles among people who inject drugs, though it can also spread through contaminated medical equipment, and rarely through sexual contact. Mother-to-child transmission during childbirth is possible but uncommon. Screening of blood products has made transfusion related infections rare. About 10% of cases have no identified source.
What makes hepatitis C insidious is its stealthy nature. Many people with hepatitis C don’t have symptoms, and acute hepatitis with jaundice is rare, occurring in only about 10% of infections. The symptoms that do appear—fatigue, mild flu-like feelings—are easily dismissed. Meanwhile, the majority of people (60-70%) develop chronic infection. I recommend a screening blood test at least once for all adults over age 55, as they are the group most likely to have hepatitis C without an identifiable source.
The incubation period ranges widely, from 2 weeks to 6 months, typically 6 to 9 weeks. Without treatment, chronic hepatitis C can lead to cirrhosis and liver cancer over decades. Before modern treatments, it was a leading cause of liver transplants.
Treatment for hepatitis C has undergone a revolution. The old approach—interferon injections combined with ribavirin—had terrible side effects and worked in only about half of patients. Today, we have direct-acting antivirals (DAAs), which can cure more than 95% of cases with just 8-12 weeks of well-tolerated oral medication. These drugs target specific proteins the virus needs to replicate, essentially starving it out of existence. The treatment is so effective that hepatitis C is now considered a curable disease.
Prevention focuses on avoiding blood-to-blood contact. Never share needles, syringes, or any drug equipment. If you’re getting a tattoo or piercing, ensure the facility follows proper sterilization procedures. Healthcare workers should follow standard precautions with blood and body fluids. Unfortunately, there’s no vaccine for hepatitis C yet, though researchers continue working on one.
The Hepatitis B Vaccine Controversy: What’s Really Happening
Now let’s address the elephant in the room—the recent controversy over the hepatitis B vaccine for newborns. This topic exploded in the news in December 2025, and it’s worth understanding what’s currently going on versus what the science says.
The Recent Development
On December 5, 2025, the CDC’s Advisory Committee on Immunization Practices (ACIP) voted 8-3 to recommend hepatitis B vaccination at birth only for infants born to mothers who test positive for the virus or whose status is unknown. This reverses decades of policy that recommended universal hepatitis B vaccination for all newborns within 24 hours of birth.
The Arguments For Changing the Policy
Some ACIP members raised concerns about vaccine safety and parental hesitancy. Committee member Retsef Levi heralded the move as “a fundamental change in the approach to this vaccine,” which would encourage parents to “carefully think about whether they want to take the risk of giving another vaccine to their child”. The controversy includes historical concerns about possible links between the hepatitis B vaccine and conditions like multiple sclerosis, autism, and other autoimmune disorders.
What Science Actually Shows
The evidence on vaccine safety is quite robust. Concerns about multiple sclerosis emerged in France in the 1990s. Since then, a large body of scientific evidence shows that hepatitis B vaccination does not cause or worsen MS. The World Health Organization’s Global Advisory Committee on Vaccine Safety has concluded there is no association between the hepatitis B vaccine and MS. It is one of the safest vaccines studied.
As for other safety concerns, CDC reviewed VAERS reports from 2005-2015 and found no new or unexpected safety concerns. The most common side effects are minor: soreness at the injection site, headache, and fatigue lasting 1-2 days.
Why the Universal Birth Dose Matters
The scientific and medical communities have strongly opposed this policy change. The American Academy of Pediatrics states that from 2011-2019, rates of reported acute hepatitis B remained low among children and adolescents, likely explained in part by the implementation of childhood hepatitis B vaccine recommendations published in 1991.
Here’s why newborns are so vulnerable: infected infants have a 90% chance of developing chronic hepatitis B, and a quarter of those will die prematurely from liver disease when they become adults.
The “just target high-risk babies” approach has a major flaw: the CDC estimates about 640,000 adults have chronic hepatitis B, but about half don’t know they’re infected. Before universal vaccination, about half of infected children under 10 got it from their mothers—the rest contracted it through other exposures not identified by maternal screening.
The Global Context
Claims that the U.S. is an outlier don’t hold up. As of September 2025, 116 of 194 WHO member states recommend universal hepatitis B birth dose vaccination. European countries that do not recommend a universal birth dose have a much lower hepatitis B incidence rate and more robust antenatal maternal screening. The majority still recommend vaccination at two to three months.
The Bottom Line
All three types of hepatitis pose serious health risks, but we have powerful tools to prevent and treat them. Hepatitis A and B have safe, effective vaccines that have dramatically reduced disease rates. Hepatitis C, while lacking a vaccine, is now curable with modern antiviral medications.
The hepatitis B vaccine controversy highlights a broader tension in public health: balancing individual autonomy with community protection. The scientific evidence strongly supports the vaccine’s safety and the effectiveness of universal newborn vaccination in preventing a disease that can be fatal. Multiple studies, decades of safety data, and recommendations from medical organizations worldwide back this up.
For parents making decisions about their newborns, the facts are these: hepatitis B is a serious disease with a high risk of becoming chronic in infants, the vaccine is highly effective at preventing infection, and extensive safety monitoring has found it to be safe with only minor, temporary side effects. As hepatitis research continues, we’re seeing remarkable progress—from the near-eradication of hepatitis A in vaccinated populations to the transformation of hepatitis C from a chronic, often fatal disease to a curable one. These advances remind us how far we’ve come in understanding and combating these liver viruses.
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The Correlation Mirage: How Good Intentions Go Wrong in Health Debates
By John Turley
On December 8, 2025
In Commentary, Medicine
Understanding the Basics
Here’s the fundamental problem: just because two things happen together doesn’t mean one caused the other. When we say two variables are “correlated,” we’re simply observing that they move in tandem—when one goes up, the other tends to go up (or down). Causation, on the other hand, means that a change in one variable directly causes a change in the other. Think of correlation as a suspicious coincidence, while causation is a proven relationship with a clear mechanism.
The tricky part is that our brains are pattern-seeking machines. We evolved to spot connections quickly because that helped our ancestors survive. If you ate those red berries and got sick, better to assume the berries caused it rather than to wait around for a controlled study. But this mental shortcut can seriously mislead us in the modern world, especially when it comes to complex health issues.
Classic Examples That Illustrate the Problem
Let me give you some examples that show how ridiculous this confusion can get when we’re not careful. There’s a famous correlation between ice cream sales and drowning—both increase during summer months, but ice cream isn’t causing drowning. The real driver is warmer weather, which leads people to both buy more ice cream and to spend more time at beaches or swimming pools where drowning might happen. This is what researchers call a “confounding variable”—a third factor that influences both things you’re measuring.
Here’s another head-scratcher: there’s a correlation between the number of master’s degrees awarded and box office revenue. Does getting more education somehow boost movie sales? Of course not. This is what we call a spurious correlation—a completely coincidental relationship that exists in the data but has no meaningful connection in reality.
Here’s good news for us coffee drinkers. For years, studies suggested a correlation between heavy coffee drinking and heart disease. Later research found the real issue: heavy coffee drinkers were also more likely to smoke. Once smoking was controlled for, coffee itself did not increase heart risk.
Perhaps the most amusing example is the correlation between stork populations and birth rates in Germany and Denmark spanning decades. As the stork population fluctuated, so did the number of newborns. Now, you could construct a “Theory of the Stork” claiming that storks deliver babies, but the real explanation probably involves other variables like weather patterns, urbanization, or environmental developments that affected both populations.
The medical field offers more serious examples. You observe a strong correlation between exercise and skin cancer cases—people who exercise more seem to get skin cancer at higher rates. Without digging deeper, you might panic and conclude that exercise somehow causes cancer. But the actual explanation is far more mundane: people who exercise more tend to spend more time outdoors in the sun, which increases their UV exposure. The confounding variable here is sun exposure, not the exercise itself.
The Vaccine-Autism Controversy: A Cautionary Tale
Now let’s talk about one of the most damaging correlation-causation confusions in recent medical history: the claim that vaccines cause autism. Many childhood vaccines are administered at the same ages when numerous developmental conditions first become noticeable—including autism, seizure disorders, and certain metabolic or genetic issues. This is a textbook case of how mistaking correlation for causation can have real-world consequences.
The whole mess started in 1998 when Andrew Wakefield, a gastroenterologist at London’s Royal Free Hospital, published a paper in The Lancet describing 12 children, eight of whom were reported as having developed autism after receiving the MMR vaccine. Here’s the thing: this wasn’t even a proper study that could establish causation. It was described as a consecutive case series with no control group or control period—it was simply a description that couldn’t tell you whether one thing causes another.
But why did this idea catch fire so dramatically? The timing created a perfect storm for correlation-causation confusion. Autism becomes apparent early in childhood, around the same time children receive many vaccines and there will be a temporal relationship by chance alone. Parents naturally searched for explanations, noticed the temporal proximity, and drew what seemed like an obvious conclusion.
The scientific community took these concerns seriously and conducted extensive research. Despite overwhelming data demonstrating that there is no link between vaccines and autism, many parents remain hesitant to immunize their children because of the alleged association. Study after study found no connection. A study of over 500,000 children in Denmark, published in The New England Journal of Medicine in 2002 found no relationship between autism and MMR as did a subsequent Danish study published in 2019. In April 2015, JAMA published a large study analyzing health records of over 95,000 children, including about 2,000 who were at risk for autism because they had a sibling already diagnosed. It confirmed that the MMR vaccine did not increase the risk for autism spectrum disorder.
The original Wakefield study eventually collapsed under scrutiny. The Lancet retracted the article, and Wakefield was found guilty of deliberate fraud—he picked and chose data that suited his case and falsified facts. Wakefield lost his license to practice medicine after being sanctioned by scientific bodies. But by then, the damage was done.
Here’s the correlation-causation issue in stark terms: the prevalence of autism has increased over time, which researchers and healthcare professionals explain is likely due to multiple factors, including people becoming more aware of autism, improved screening, and updated and expanded diagnostic criteria to include other conditions on the autism spectrum. Meanwhile, immunizations have increased and have dramatically reduced the incidence of vaccine-preventable diseases. These two trends—increasing autism diagnoses and increasing vaccination rates—happened to occur during the same historical period, creating an illusory correlation.
The real causes of autism are complex. There is no single root cause; a combination of influences is likely involved, including certain genetic syndromes, genetic changes affecting cell function, and environmental influences such as premature birth, older parents, and illness during pregnancy. Vaccines simply aren’t part of that picture.
Other Health-Related Confusion
The vaccine-autism controversy isn’t the only place where correlation-causation confusion causes problems in health contexts. Let me give you a few more examples that show how pervasive this issue is and how difficult it can be to distinguish between correlation and causation.
Consider the relationship between diet and health outcomes. The amount of sodium a person gets in their diet is closely correlated to the total calories they eat—in other words, the more a person eats, the more sodium they’re likely to take in, and eating a lot of calories often leads to obesity. Both obesity and high-sodium diets are believed to contribute to high blood pressure. So, what’s the primary driver? Is it sodium, excess calories, or obesity? These are exactly the kinds of questions researchers must carefully untangle.
Here’s another tricky one: research has shown a correlation between antibiotic use in children and increased risk of obesity, with greater antibiotic use associated with higher obesity risk, particularly for children with four or more exposures. But this correlation alone doesn’t tell us whether antibiotics cause obesity. There could be multiple explanations: perhaps children who need frequent antibiotics have other health issues that predispose them to weight gain, or perhaps the infections themselves (not the antibiotics) are the real issue, or maybe it’s actually a disruption of gut bacteria that matters. Without understanding the exact physiological mechanism, we can’t design effective interventions.
Similarly, increased BMI seems to be associated with an increased risk of several cancers in adults. But it would be erroneous to conclude that simply being overweight directly causes cancer. Socioeconomic factors, environmental toxins, access to healthcare, lifestyle differences, physical activity levels, and diet all intertwine in complex ways. Some people may face multiple risk factors simultaneously, making it difficult to isolate which factors are most significant.
When cell phones first became widely used, there was an increasing concern that radiation from the cell phones was causing brain cancer. Brain cancer rates have remained stable for decades despite exponential increases in cell-phone use—strong evidence against a causal relationship.
Beyond Statistics
The stakes here go way beyond academic accuracy. When people confuse correlation with causation in health contexts, they make decisions that can harm themselves and others. The 2017 measles epidemic in Minnesota’s Somali community was in no small measure fomented by Wakefield—he didn’t fade away quietly. He and other anti-vaxers repeatedly proselytized to the community, leading to an approximately 45% reduction in vaccination. At the same time there was an increase in autism diagnoses. Think about that: vaccination rates dropped, yet autism diagnoses continued to rise—the exact opposite of what you’d expect if vaccines caused autism. A word of caution: this is an observation, not a carefully controlled study.
The problem extends to how we evaluate new treatments and risk factors. In clinical medicine, there are treatment protocols in use that are not supported by randomized controlled trials. There are risk factors that have been associated with various diseases where it’s difficult to know for certain if they are actually contributing causes. This uncertainty creates space for misunderstanding.
How Scientists Establish Causation
So, how do researchers move from observing a correlation to proving causation? They look for several key elements. These include: a stronger association between variables (which is more suggestive of cause and effect than a weaker one), proper temporality (the alleged effect must follow the suspected cause), a dose-response relationship (where increasing exposure leads to proportionally greater effects), and a biologically plausible mechanism of action.
The gold standard is the randomized controlled trial, where researchers can carefully control for confounding variables by randomly assigning people to treatment and control groups. For ethical reasons, there are limits to controlled studies—it wouldn’t be appropriate to use two comparable groups and have one undergo a harmful activity while the other does not. That’s why we often rely on observational studies combined with careful statistical methods to rule out alternative explanations.
The Bottom Line
Understanding the difference between correlation and causation isn’t just an academic exercise—it’s a critical thinking skill that helps you navigate health claims, news stories, and medical decisions. The vaccine-autism controversy shows how dangerous it can be when we mistake coincidental timing for causal relationships, especially when those misunderstandings spread through communities and lead to preventable disease outbreaks.
The key takeaway? When you see two things happening together, your brain will want to assume one caused the other. Resist that urge. Ask yourself: could there be a third factor driving both? Could the timing just be coincidental? Is there a clear, testable mechanism that would explain how one causes the other? These questions can help you separate meaningful connections from statistical coincidences—and potentially save you from making poor health decisions based on faulty reasoning.