In making the case for a national vaccine registry to raise immunizations to as much as 95% — the level deemed necessary to protect the entire community through herd immunity —health reporter Genna Buck unluckily cites the Quebec measles outbreak of 2011 in the current issue of Maclean’s, Canada’s only newsweekly.
“During the last Quebec outbreak, in 2011, a single “super-spreader” (one highly social person who was particularly talented at infecting others) was responsible for 678 measles cases. There’s nothing—yet—to prevent that from happening again,” she writes, her “yet” an ominous warning of the consequences of not reaching the 95% level, at which the remaining 5% of the “herd” would be protected.
Buck was unlucky in citing the Quebec measles outbreak because it utterly disproves her case, and especially the case of the CD Howe Institute, whose recommendations Buck was describing. The Quebec outbreak was not just any outbreak, its total of 776 cases was the largest epidemic in North America in a decade, well exceeding the current tally for the entire post-Disneyland period and making Quebec’s one of the most studied epidemics of our times. CD Howe’s argument doesn’t stand up to scrutiny precisely because Quebec’s experience shows herd immunity, and government-mandated vaccinations, aren’t the no brainers CD Howe imagines.
The population in Quebec actually exceeded the levels required for herd immunity — the epidemic “was unexpected given the province’s documented immunization coverage,” wrote Gaston de Serres, an infectious diseases specialist with Quebec’s provincial public health agency in the Journal of Infectious Diseases.
Not only did Quebec’s high vaccination rate fail to protect the unvaccinated members of the herd, it didn’t protect very large numbers of those who were vaccinated. Worse, the vaccine actually backfired on many whose parents had complied with the public health authorities. Teens who received their first shot at age one — as recommended by public health authorities — were six times likelier to be infected than children whose parents delayed the first shot, according to de Serres. It is even possible, he speculated, that the Quebec outbreak was fuelled by vaccinating children at too young an age, a view shared by Dr. Diane Griffin, a measles expert at Johns Hopkins Bloomberg School of Public Health in Baltimore.
But the problem extends beyond that first shot. Referring to another of his studies, this one in the journal, Pediatrics, de Serres noted that “there is vulnerability in children who receive two doses and we should not overlook that. The reason for that is still unknown. But it is important to dig into this question further.” In examining the high school at the center of the 2011 epidemic, which contributed nearly one-quarter of all cases among adolescents and had a vaccination rate above 95%, de Serres had found that “nearly half (48%) of the cases in this school outbreak were due to vaccine failures in 2-dose recipients.”
Does herd immunity exist? Not at the level claimed by CD Howe and Maclean’s Buck, because vaccines aren’t forever — their effectiveness wanes, leaving unsuspecting people vulnerable. In an earlier, 1989 epidemic Quebec attained 99% coverage. As de Serres concludes, “even 100% 2-dose coverage would barely meet the level of immunity required for elimination. The large proportion of cases in adolescents and the small proportion in preschoolers and elementary school children suggest a problem of waning immunity.”
Maclean’s and Genna Buck require two Band-Aids for perpetuating the myth that herd immunity can be counted on to protect the population. Their coverage of the CD Howe report included not a single expert who dissented from the conventional, yet unproven, wisdom of herd immunity.