Where Do They Find These Scary Statistics III – Let’s Make a Few Assumptions – Hepatitis B
Parents have questions about the risk-benefit equation of the Hepatitis B vaccine. It is possible for a parent to be quite certain that their infant is not at risk of prenatal or birth exposure to this disease. The risk factors for exposure during infancy, early childhood, and the elementary school years can be reasonably well assessed on an individual basis.
But very little of the discussion around this vaccine addresses individual risk factors. Instead, the focus is on the population as a group, which is assumed to benefit from a lowered level of circulating disease as a result of infant vaccination. When we look at two of the three news articles published to promote the studies claiming lifesaving achievements for vaccination, they deliver positive press for the hepatitis B vaccine:
Occurrences and mortality associated with hepatitis B were reduced by about 80%. Infectious Disease News
Obvious question: who were the beneficiaries of this reduction, and is there evidence that universal vaccination of babies is the cause of the drop in occurrences and mortality? The program to screen pregnant women for hepatitis B started at the same time as the universal vaccination of babies.
The numbers don’t account for chronic disease averted because of a prevented infection: Hepatitis B, for example, is a major risk factor for liver cancer. Time
Without knowing how many babies are actually at risk of infection, it is hard to know how much chronic disease has actually been prevented by vaccinating babies.
The generalities in these news articles are not useful to real life parents trying to decide if their baby needs a birth dose of this vaccine.
If parents turn to their pediatrician for advice, will the pediatrician look at the risk-benefit equation for that particular baby, or will they be focusing on populations? And how important is the hepatitis B vaccine for the general health of the population in the U.S.? Why is this vaccine recommended for universal use among babies and children in the United States?
A common theme when vaccines are discussed:
Schuchat thinks today’s young parents don’t realize how bad the 1950s were for kids before there were a lot of vaccines to prevent illness.
But Hepatitis B wasn’t an epidemic disease for children in the 1950s. It has never been an epidemic disease for children in the United States. Let’s review the facts:
In the United States, Western Europe, and Australia, HBV infection is a disease of low endemicity. Infection occurs primarily during adulthood, and only 0.1% to 0.5% of the population are chronic carriers. Lifetime risk of HBV infection is less than 20% in low prevalence areas. (see page 7)
So why is this vaccine routinely given to almost all newborns in the United States? Does this vaccine save children’s lives?
According to the same two studies we considered in the previous blogs in this series, and widely quoted in the press to support mass vaccination of infants, the answer is definitely, certainly, absolutely! The only hitch is that the two studies disagree drastically on the numbers being saved, a detail left out of the various news stories. The two studies are: Historical Comparisons of Morbidity and Mortality for Vaccine-Preventable Diseases in the United States, which was published in the Journal of the American Medical Association in 2007. Author Affiliations: National Center for Immunization and Respiratory Diseases (entity formerly known as the “National Immunization Program”); Centers for Disease Control and Prevention, and Economic Evaluation of the 7-Vaccine Routine Childhood Immunization Schedule in the United States, published in the Archives of Pediatrics & Adolescent Medicine in 2005. Author Affiliations: National Immunization Program, Centers for Disease Control and Prevention, Public Health Service, US Department of Health and Human Services.
For hepatitis B, the 2007 study has these numbers: prevaccine deaths/year 237, postvaccine deaths/year 47, deaths prevented 190. All of the statistics are estimates, but are based on reported cases multiplied by 2.8.
The 2005 study has these numbers: in a hypothetical birth cohort of 3,803,295 children, without vaccine 3,427 deaths, with vaccine, 403 deaths, therefore the vaccine would prevent 3,024 deaths over the lifetime of the cohort. In the vaccinated model of the cohort, the babies received three doses of the Hepatitis B vaccine. Adult exposures to the disease are not considered.
According to these two studies the answer is yes, the vaccine saves lives. But the number of lives saved is up for discussion. If we consider projected deaths, the difference between the two studies is a modest 2,834 deaths. Seventeen times as many deaths?
How did the authors of the 2005 study come up with their numbers?
In the United States, the prevalence of HB surface antigen positivity among women of childbearing age was assumed to be 0.57%, with 15% of these women being HB e antigen positive.[26,77] The prevalence of anti–HB core antibody at age 5 years is 0.56%, and the lifetime risk of HBV infection is 6.1%. We assumed that 90% of infants born to HB surface antigen–positive/HB e antigen–positive women and 10% of infants born to HB surface antigen–positive/HB e antigen–negative women become perinatally infected. We assumed that acute HB occurs in 1% of perinatal infections, 6% of early childhood infections (after birth through 5 years old), and 30% of late infections (>5 years old through adulthood). We assumed that 0.1% of infants and 0.6% of young children, adolescents, and adults who develop acute HB will develop fulminant hepatitis, and the mortality of fulminant HB is assumed to be 70%.[23-24,26,79-80] We assumed that 90% of infants, 30% of young children, and 6% of adolescents and adults who become infected will develop chronic HB infection. Long-term sequelae develop in 25% of chronic infections from perinatal or early childhood infection and in 15% of chronic infections from late infection; sequelae include chronic persistent hepatitis, chronic active hepatitis, cirrhosis, and primary hepatocellular carcinoma.[26, 79-83]
For HB, because acute cases were underreported and chronic cases were not reported to the National Notifiable Diseases Surveillance System, we decided to use an established decision tree model and the efficacy of the vaccine to estimate the likelihood of HB infection and sequelae in vaccinated and unvaccinated children in the cohort.
Compared with the 2007 study, which looked at actual symptomatic cases reported and actual hospitalizations and average deaths and actual reported acute clinical cases and then multiplied them by 2.8 for underreporting, the 2005 calculation has so many assumptions as to be impenetrable. I counted and there are sixteen assumptions in the first paragraph of the quote. Their “established decision tree model” is really an assumption tree, and the 2,834 additional deaths are based on assumptions piled up like the mattresses in the Princess and the Pea. There are a lot of feathers floating around and very few facts.
Now let’s have a look at the studies used as references to support this paragraph. The first sentence has two references. Number 77, points here: Hepatitis B: evolving epidemiology and implications for control, by Margolis HS, Alter MI, Hadler SC. We’ve only got access to the abstract. The authors were from the Centers for Disease Control.
The failure of the current immunization strategy to prevent a disease with significant health care and economic consequences is beginning to cause a reevaluation of this approach. A comprehensive approach to eliminating HBV transmission must address infections acquired during early childhood as well as those acquired by teenagers and adults.
It looks like an analysis of the immunization data. There is no mention of the actual rate of infections acquired during early childhood.
Reference 26 is used 6 times. You can look at the abstract here: Prevention of hepatitis B virus transmission by immunization. An economic analysis of current recommendations by H. S. Margolis, P. J. Coleman, R. E. Brown, E. E. Mast, S. H. Sheingold and J. A. Arevalo. Again, the authors were from the CDC.
A decision model was used to determine the incremental effects of the following hepatitis B immunization strategies in a birth cohort receiving immunization services in the public sector: (1) prevention of perinatal HBV infection, (2) routine infant vaccination, or (3) routine adolescent vaccination. (emphasis added)
This reference, which is used 6 times in the paragraph on hepatitis B, points not to a study, but to the same type of theoretical analysis used in the 2005 article. More feathers.
Prevalence of Hepatitis B Virus Infection in the United States: The National Health and Nutrition Examination Surveys, 1976 Through 1994 by Geraldine M. McQuillan, PhD, Patrick J. Coleman, PhD, Deanna Kruszon-Moran, MS, Linda A. Moyer, RN, Stephen B. Lambert, MS, and Harold S. Margolis, MD is reference number 78 and is available as full text.
In both surveys, the prevalence of hepatitis B virus infection was low until 12 years of age, when it increased in all racial groups…
In both surveys and in all racial/ethnic groups, the prevalence of hepatitis B virus infection did not begin to increase until puberty, suggesting that sexual transmission is the primary mode of spread in the United States.
Data from NHANES demonstrate that children have a low but appreciable risk of hepatitis B virus infection that increases significantly at adolescence, presumably with the onset of sexual activity and other high-risk behaviors; this supports the need to routinely vaccinate.
This time we don’t have feathers. It is a real study, doing real testing, and looking at the real prevalence. The problem with the study in this context is that it doesn’t provide data that supports universal newborn vaccination with the hepatitis B vaccine. I’ll leave it to my readers to follow up on the other seven articles referenced in the relevant paragraph.
To return to our starting point, it is possible for a parent to make an evidence-based decision not to vaccinate their newborn infant for hepatitis B. The data in the 2005 study claims that 3,024 lives are saved each year because of universal newborn hepatitis B vaccine in the United States. The data in the 2007 study claim that 190 lives are saved each year. The difference in the two numbers seems to derive from an amazing tolerance for feathers in one set of authors and an interest in data in the other set of authors.
Remember Dr. Gerberding talking about the 33,000 lives saved each year by routine vaccination in the United States? Data or feathers?