The media is reporting as fact that the Hib vaccine protects against leukemia, but what is the actual evidence for this?

The New York Times asserts as fact that vaccinating children for Haemophilus influenza type B (Hib) reduces the risk for for acute lymphoblastic leukemia (ALL).  Science Daily makes the same claim, asserting that “the cancer protection offered by the Hib vaccine has been well established in epidemiological studies”.

Both articles refer to a study published in Nature Immunology by Dr. Markus Müschen, et al, titled “Mechanisms of clonal evolution in childhood acute lymphoblastic leukemia“. As the Times notes, when children “are exposed to Hib early in life — in day care, for example — their immune response is usually, but not always, well controlled, fighting the bacterium without causing serious illness.”

The Times goes on, explaining the mechanism by which early exposure protects against leukemia:

But using a mouse model, Dr. Müschen and his colleagues found that in some cases, infection with the HiB bacterium triggers a vigorous immune reaction that activates two enzymes. These enzymes can cause mutations in certain types of blood cells, driving them into malignancy. When this happens, children are more likely to develop leukemia when they are 5 to 7 years old.

It closes by quoting him saying, “Whatever activates the immune system early in life reduces the risk for ALL.”

I found this closing comment interesting, as, this being the case, then natural infection with Hib would provide the same protective benefit.

Yet the Times relays Dr. Müschen’s claim that “the effect of the vaccine was a 20 percent reduction in risk for leukemia.” Science Daily quotes Müschen saying,

Hib and other childhood infections can cause recurrent and vehement immune responses, which we have found could lead to leukemia, but infants that have received vaccines are largely protected and acquire long-term immunity through very mild immune reactions.

So, to be able to say that vaccination reduces the risk of this cancer, they must have studied incidence of leukemia in children who received the Hib vaccine versus children who did not, right?

With these questions in mind, I clicked through to the study. It states (emphasis added):

It has been hypothesized that delayed exposure of infants to infections in the highly protective environments of developed societies causes protracted and excessive immune responses with substantial collateral damage. Early exposure to common infections (such as via attendance at a daycare facility) mitigates this risk.

So there it is again. Again, how is this not equally true for natural infection?

The paper continues (emphasis added):

The systematic introduction of vaccination programs during early childhood has reduced the incidence of ALL, presumably by reducing chronic infections and the immune responses that they instigate. For example, the administration of vaccine against Haemophilus influenzae type b in early childhood significantly reduced the risk of childhood ALL in three different case-control studies of American, Finnish and Canadian cohorts.

So I turned to the footnotes and found the three studies cited to support this claim.

Study #1

The first is a study published in the British Journal of Cancer in October 2000 titled “Haemophilus influenzae type B vaccination and risk of childhood leukaemia in a vaccine trial in Finland“. It did not examine incidence of leukemia in Hib-vaccinated versus unvaccinated children. Rather, it compared children who’d received a series of doses starting at three months with children who’d received a single dose at age two. They did find that incidence of leukemia was lower in the former group than the latter, “but the difference did not reach statistical significance” (emphasis added). They hence called for further studies.

So that study doesn’t support Müschen’s claim.

Study #2

The second is another study published in the British Journal of Cancer in August 2001 titled “Haemophilus influenzae type b serology in childhood leukaemia: A case–control study“. It also did not compare incidence of leukemia in vaccinated versus unvaccinated children. Rather, they compared the antibody levels — which would indicate exposure to HiB — in children who had the cancer with children who did not, and plotted it as a function of age. What they found is what the Times already informed us, that earlier exposure to Hib is associated with a decreased risk of developing leukemia.

So what does any of that have to do with the Hib vaccine?

Answer: Nothing.

The serum samples they used to test for antibody concentrations were all collected from children between 1966 and 1970. The first Hib vaccine wasn’t licensed until 1985 and wasn’t introduced into Canada until 1988. As the authors point out, for neither group, therefore, could antibody levels be attributed to Hib vaccination.

So there is the answer to one of my questions: Indeed, the protective effect observed was a result of natural infection with HiB, not vaccination.

The only thing this study has to do with the vaccine is that the authors hypothesized that since early exposure was associated with a reduced risk of cancer, therefore early vaccination might help to prevent cancer. They did not test this hypothesis.

So, that study doesn’t support Müschen’s claim, either.

Study #3

So we come to the third study cited to support the claim that HiB vaccination is associated with reduced risk of cancer. It is a 2005 study published in the International Journal of Epidemiology titled “Vaccination history and risk of childhood leukaemia“.

It’s interesting to note, in light of Science Daily’s claim that it is “well established” that the vaccine offers a protective effect against leukemia, this study’s statements that “a few studies have reported a decreased risk” while “several studies found no evidence of an association between vaccination and the risk of childhood leukaemia” (the studies they refer to in both cases were not limited to Hib). Indeed, it was this inconsistency of findings from previous studies that prompted their own research.

Not so “well established”, after all, it seems…

So we know that early natural infection is associated with a decreased risk of leukemia. Keeping that in mind, it is crucial to emphasize that this study, like the others, did not compare incidence of the cancer in children who’d been vaccinated with children who had not.

In fact, “there were very few children who were not vaccinated” in the study. What they did instead was to compare the risk-mitigation effect in terms of the number of doses that children received. Only 5.3% of study cases and 4.9% of controls (children without leukemia) were unvaccinated. These unvaccinated children were lumped together with children who had received one or two doses of the Hib vaccine and compared with children who’d received the full recommended schedule of three or more doses.

What they found was that receiving the higher number of doses was associated with a decreased risk of leukemia compared to the lower number of doses.

From that finding, they state their conclusion: “Hib vaccination is associated with a reduced risk of childhood leukaemia.”

That does not follow. A finding of decreased risk for a greater number of doses compared with a fewer number of doses is not the same as a finding of decreased risk for vaccination versus no vaccination. To draw the latter conclusion from the former observation is a logical fallacy (non sequitur). The statement is false.

The Hygiene Hypothesis

Further insight can be found in another study, “A meta-analysis of the association between day-care attendance and childhood acute lymphoblastic leukaemia“, published in 2010 in the International Journal of Epidemiology. They note that it is the “delay in exposure to common infectious agents during early childhood” that is hypothesized to result in “insufficient priming of the immune system“, which in turn can lead to the development of leukemia in a small number of individuals who did not develop this early immunity (emphasis added).

Since the “improved socio-economic conditions may lead to delay in exposure to infections”, this would explain why there is a “notably higher incidence” of the most common subtype of leukemia “with its characteristic peak age between 2 and 5 years observed only in more socio-economically developed countries”.

So the authors did a meta-analysis of existing studies that tested this hypothesis by looking at whether children who attended day-care and hence were at higher risk of exposure to pathogens had a lower risk of developing leukemia. What they found was that, indeed, day-care attendance was associated with a reduced risk of leukemia, with a few of the studies showing that the strongest reduction in risk occurred when children started attending day-care at under 6 months of age and a couple of others showing that spending a greater number of hours in day-care also reduced the risk.

This has implications for vaccine theory and its associated vaccine-induced “herd immunity” theory, which must be considered in light of the observed protective effect against the development of leukemia of early Hib infection.

Long-Term Effects of Vaccination

Before the Hib vaccine was developed, as the CDC notes, it was a common childhood infection. While there are six known encapsulated strains (a-f), as well as nontypeable strains, “type b organisms accounted for 95% of all strains that caused invasive disease.” Pretty much everyone was infected as a child, but most people showed no symptoms, and full immunity was generally acquired by the age of 5 or 6. For the vulnerable age of less than 6 months, before the child had an immune system developed enough to be able to handle the infection on its own, breastfeeding provided protection through transferred antibodies from the mother.

This has all changed as the result of widespread vaccination.

Graph showing the increase in invasive H. Influenzae infection (Ruback, et al)

Graph showing the increase in invasive H. Influenzae infection using two different data sets (Ruback, et al). Click to enlarge.

Hib used to be the most common cause of bacterial meningitis in children under 5. Since the introduction of the vaccine, “the incidence of invasive Hib disease in children has decreased by 99%”. However, as noted in a 2011 study published in Emerging Infectious Diseases, invasive H. influenzae infections among adults is increasing, and invasive disease caused by the bacteria is disproportionately affecting the elderly, in whom there is an associated high mortality rate.

The researchers looked at incidence in Utah as reported during the decade from 1998 until 2008. What they found was that incidence of invasive infection increased over this period, and particularly among people 65 or older — a trend similar to those reported by other studies in other states.

Moreover, widespread vaccination has resulted in a shift in the prevalent strain of H. influenzae (which is misnamed, by the way, because the flu is caused by any number of viruses, not bacteria, as was discovered after this organism was given its name). The authors note that non-b encapsulated strains accounted for 49% of cases and nontypeable strains 43%, while Hib accounted for only 9%.

Graph showing how invasive H. influenzae disease is disproportionately affecting the elderly (Rubach, et al). Click to enlarge.

Graph showing how invasive H. influenzae disease is disproportionately affecting the elderly (Rubach, et al). Click to enlarge.

The obvious reason for this is that childhood infection with Hib conferred permanent immunity not only against type b, but all strains of H. influenzae. Now, in the vaccine era, this permanent, non-specific immunity has been lost. (I won’t get into it, but vaccines favor humoral immunity, i.e., an antibody response, at the expense of the more robust cell-mediated immunity. Vaccines do not confer the same kind of immunity as natural infection.)

Indeed, the authors explicitly state that this could be caused by “changes in the organisms” (implying that vaccine use has caused adaptation of the bacteria and increased the prevalance of non-type b strains), “changes in the number of persons at high risk” (implying that they no longer have the lifelong immunity conferred by childhood infection), or “waning of cross-immunity induced by exposure to Hib.”

Moreover, 22% of cases resulted in death, two-thirds among those 65 or older, and the death rate did not differ significantly by serotype (meaning, e.g., type a could be just as deadly as type f).

Graph showing the number of invasive H. influenzae infections among adults by serotype (Rubach, et al). Click to enlarge.

Graph showing the number of invasive H. influenzae infections among adults by serotype (Rubach, et al). Click to enlarge.

The authors point out that “Despite the virtual elimination of Hib in areas with widespread use of Hib vaccine, invasive disease caused by H. influenzae remains a major source of illness and death.” While the prevalence of Hib has decreased, other encapsulated serotypes “seem to have emerged as major causes of invasive disease”. While nontypeable strains used to be considered “a relatively noninvasive bacteria”, it now has an “emerging role” in the development of invasive disease.

The authors also note that under-reporting is likely and that there is no vaccine to protect against non-type b strains of the bacteria.

The fact that the vaccine, unlike natural infection, does not confer permanent immunity also raises the question of whether mothers now are able to confer protection to their infants via breastmilk. We know now, for example, that in the case of measles (which is a virus, not a bacteria), vaccine policy has shifted the risk from children in whom it is generally a mild disease to more vulnerable infants because mothers born into the vaccine era, unlike their mothers and/or grandmothers, were not exposed naturally as children and hence did not develop the permanent immunity of natural infection. As vaccine-induced immunity wanes, they are no longer able to offer the same protection to their babies via breastmilk, leading to the ironic situation that vaccine policy has increased the risk to infants in the event of measles outbreaks, which can and do occur in highly vaccinated populations.

Conclusion

While the New York Times and Science Daily report as fact that the Hib vaccine confers protection against leukemia, the study they refer to does not itself examine whether this is true or not. The authors of that study simply assumed so and set out to study the possible mechanism by which this protection might be conferred.

To support the assumption, the authors cited three previous studies, none of which actually support the claim: 

  • The first found no statistically significant association.
  • The second wasn’t even relevant, except inasmuch as it showed that natural infection at a younger age, as opposed to exposure to antigen from the Hib vaccine, is what conferred the protective effect against the cancer — a finding that Müschen, et al, are curiously silent about while citing this study to support their assumption.
  • The third drew a conclusion that does not follow from its findings. It did not compare incidence of leukemia in children who’d received the vaccine with children who had not. It does not follow from their finding that children who’d received three or more shots had less risk of developing leukemia than those who’d received two or fewer shots that therefore children who are vaccinated have less risk than children who are not.

Neither that study’s authors nor Müschen, et al, considered whether receiving the first two doses, but not following up with the third recommended booster shot, might actually be associated with an increased risk of developing leukemia compared to the already-observed protective effect of early natural exposure due to the waning immunity of the vaccine (hence the recommendation for a third booster).

Neither study examined the question of whether, given the observed protective effect of early natural exposure, vaccine policy ought not be reconsidered in light of its effect of virtually eliminating the early childhood exposure that would otherwise confer this protective effect against leukemia, or in light of its population-wide effect of shifting the risk to the elderly with an associated high mortality rate, or in light of how it has shifted bacteria prevalence into vaccine-resistant strains, how it could potentially cause an evolution into even more virulent strains, etc.

Instructively, the authors of the study showing that invasive H. influenzae infections are actually on the rise and disproportionately affecting the elderly conclude by suggesting that we need even more vaccines to solve these new problems caused by the existing one.

In sum, we have an illustration of the institutional myopia that exists when it comes to vaccines. Researchers study vaccines through the lens of public policy. The media reports about the issue through the same narrow perspective, demonizing any heretical views that don’t conform with the vaccine religion as though there wasn’t even a discussion to be had. A line from the U2 song 11 O’Clock Tick Tock comes to mind:

“We thought that we had the answers. It was the questions we had wrong.”

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