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Vaccination uptake: access is still biggest barrier, experts warn

BMJ 2019; 366 doi: (Published 17 September 2019) Cite this as: BMJ 2019;366:l5576

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The Boiling Frog Principle: patient safety and vaccines

Recent comments by Elisabeth Mahase, Helen Haskell, Stuart Fletcher, Noel Thomas , John Stone and JK Anand about patient safety and vaccines prompt the following reflections about an old metaphor:

The Boiling Frog Principle is a metaphor for the fact that we fail to appreciate the pathology that results from environmental hazards which creep gradually upon us. I first learned about the BFP during the infant formula controversy of the 1970s and early 1980s. It was especially apt in the US where the marketing of proprietary infant formula had been so successful and where so few infants were breastfed. During this period I published epidemiologic research that raised awareness of the benefits of breastfeeding in developed nations, and of the morbidity associated with formula feeding. (Cunningham: Pediatrics 1972;50:823. J Pediatr 1977;90:721…et al.) I well remember the initial response of pediatric colleagues, most of whom could not believe that formula was inferior to human milk.

It now strikes me that we have a similar situation with vaccinations. Our immunization programs have gradually expanded over the last 70 years, and distribution of large numbers of vaccines to children is virtually universal. There have been some notable successes, but our knowledge of long-term vaccine effectiveness and adverse effects is quite limited. We have taken on faith that, as a whole, immunization programs have done much more good than harm, but we do not know with any precision where the overall balance between risks and benefits really lies when every vaccine is given to every child. With universal vaccination it is likely that we are unaware of existing hazards, just as we were unaware of the hazards of infant formula. The list of potential vaccine adverse effects may be long, but I think of certain ‘mystery diseases’: Kawasaki disease, SIDS, autism, and acute flaccid myelitis/AFM. These have been associated with vaccination, but because of the way vaccines have been developed, tested, licensed and marketed there has been no opportunity to do the unbiased and properly controlled trials to support or exclude a causal role for vaccines—notwithstanding the observational studies used to assert non-causality in these diseases.

Many vaccine authorities will find the foregoing suggestions outrageous, but they will make good sense to those who have studied “non-specific vaccine effects.” DPT vaccine, for example, is associated with an increase in all-cause mortality in poor countries, even though it prevents the target diseases. BCG and measles vaccines, on the other hand, have been associated with decreased all-cause mortality, well beyond their specific prevention of TB and measles. In these examples a non-specific, or ‘heterologous’ effect on the immune system is postulated. The BMJ has published articles about NSVE going back more than 25 years and has been exceptional in bringing the subject to light, including studies by Peter Aaby, Christine Benn, Frank Shann, Paul Fine, Andrew Pollard, and others. They have called for randomized trials of different vaccine schedules in the hope that the optimal schedule can be found, minimizing the harms and maximizing the benefits of NSVE, while also providing specific protection against the target diseases. These authorities, at least, have not taken the safety of current immunization schedules completely for granted.

Properly controlled trials have become more and more important with every new vaccine. Natasha Crowcroft and her colleagues emphasize that new technologies bring considerable uncertainty about safety and effectiveness, requiring many years for adverse events caused by vaccines to be identified and confirmed. (BMJ 2015;350:h308)

The foregoing medical opinions have been reinforced by one legal scholar, who has called for an overhaul of US vaccination laws. I paraphrase what Efthimios Parasidis says about the National Childhood Vaccine Injury Act of 1986: Just as the health benefits of vaccines cannot be seriously questioned, the shortcomings of the legal framework governing immunizations cannot be ignored. The Vaccine Act was established when there were fewer vaccine doses, when health information technology was in its infancy, and when lawmakers heavily favored corporate welfare and deregulation over consumer protection. The result is that manufacturers have enjoyed robust immunity from tort claims for vaccine-related injuries. Furthermore, once a vaccine is approved and marketed, a manufacturer does not have a statutory obligation to actively collect and analyze safety and efficacy data, and is under no obligation to update vaccine formulas in light of new scientific advancements. Parasidis proposes that the requirements for adverse event reporting and post-market analysis of vaccine safety and efficacy be toughened. He also proposes that the law be recalibrated to remove the nearly insurmountable barriers in Vaccine Court to fair compensation for vaccine injuries. (Parasidis, “Recalibrating Vaccination Laws.” Boston University Law Review 2017;97:2153)

The boiling frog metaphor is a whimsical but serious warning against complacency and easy assumptions about patient safety and potential environmental hazards, medical or non-medical.
ALLAN S. CUNNINGHAM 19 September 2019

Competing interests: No competing interests

19 September 2019
Allan S. Cunningham
Retired pediatrician
Cooperstown NY 13326 USA <>