Mass vaccination advocates rely on ‘herd immunity’ to make their case. But it doesn’t exist.

This article, by Lawrence Solomon, was first published by the Financial Post

“When vaccination rates are very high, as they still are in the nation as a whole, everyone is protected,” explained USA Today in a recent editorial entitled “Vaccine opt-outs put public health at risk.”

“This ‘herd immunity’ protects the most vulnerable, including those who can’t be vaccinated for medical reasons, infants too young to get vaccinated and people on whom the vaccine doesn’t work. But herd immunity works only when nearly the whole herd joins in. When some refuse vaccinations and seek a free ride, immunity breaks down and everyone is more vulnerable.”

The concept of “herd immunity” first materialized in the 1930s, when Johns Hopkins University’s Arthur Hedrich discovered that, after 55% of Baltimore’s population acquired measles (and thus immunity to measles), the rest of the population, or “herd,” became protected. This concept provides today’s rationale for insisting that everyone be vaccinated.

Measles outbreaks occur even when the vaccinated population exceeds 95%

“If you only risked your own health by not getting vaccinated, that would be your business,” mass vaccination advocates state. “But when your failure to get vaccinated endangers me or my child, that becomes my business.” It’s a powerful argument, except for one thing — herd immunity in vaccinated populations has been repeatedly disproven.

In November 1966, in announcing a mass vaccination program for measles that would exceed the 55% level reached in Baltimore, the U.S. Public Health Service confidently announced that “Effective use of these vaccines during the coming winter and spring should insure the eradication of measles from the United States in 1967.”

When measles failed to be eradicated, public health experts decided that a 70% or 75% vaccination rate would secure herd immunity. When that proved wrong, the magic number rose to 80%, 83%, 85%, and then it became 90%, according to a 2001 Health Services Research report. Later health experts commonly cited 95%.

But that too was insufficient — measles outbreaks occur even when the vaccinated population exceeds 95%, leading some to say a 98% or 99% vaccination rate is needed to protect the remaining 1% or 2% of the herd. But even that may fall short, since outbreaks occur in fully vaccinated populations.

“The target would be to have 100% of the population vaccinated,” Dr. Gregory Taylor of the Public Health Agency of Canada recently told CBC, voicing an increasingly common perspective among public health professionals. At that point, the balance of the herd that would be protected through mass vaccination would be precisely 0.

But even vaccinating 100% of the population wouldn’t be enough, say scientists at the Mayo Clinic’s Vaccine Research Group, because the measles vaccine is a dud with some people, offering no protection at all, and its effectiveness wanes with others, even if they get boosters. According to Tetyana Obukhanych of Stanford University’s School of Medicine, the measles vaccine works as planned with only 25% of the population, leaving the majority of adults who have been vaccinated as children with little or no protection. Up to half of today’s cases involve adults.

Unlike childhood measles, adult measles is dangerous: 25% of cases require hospitalization. Measles is especially dangerous when contracted by expectant mothers — studies of hospital outcomes in Los Angeles and Houston found that most suffered serious complications, some died, and their babies often died in the womb.

The dangers extend to infants who, as USA Today points out, are too young to be vaccinated. These entirely helpless members of “the herd” depend on antibodies inherited from their mothers. Yet previously vaccinated mothers have few antibodies to pass on, depriving their babies of protection. The only tried-and-true way for mothers to safeguard their infants — those most at risk of death from measles — remains nature’s way: by ensuring that the mother had previously contracted natural measles.

In fact, herd immunity — so elusive today — fully existed prior to the vaccine’s introduction. Virtually 100% of the population then contracted measles, typically as children, giving everyone lifelong immunity — and future mothers the means to protect their offspring. In mass vaccinating us, scientists of the 1960s didn’t realize that infecting us with the measles vaccine — a weak version of the natural measles virus — would give us a weak version of the defenses our bodies develop to the real thing.

Ironically, the Public Health Service considered measles generally benign in the pre-vaccine era. “Complications are infrequent and, with adequate medical care, fatality is rare…. Immunity following recovery is solid and lifelong in duration,” its chief of epidemiology, Alexander Langmuir, acknowledged in “Epidemiologic basis for eradication of measles in 1967.”

Why, then, did he decide to eradicate this generally harmless and beneficial disease? “To those who ask me, ‘Why do you wish to eradicate measles,’ I reply with the same answer that Hilary used when asked why he wished to climb Mt. Everest. He said, ‘Because it is there.’ To this may be added, ‘…and it can be done.’”

Herd immunity sounds fine in theory. But as Stanford’s Dr. Obukhanych concluded, “As with any garbage in-garbage out type of theory, the expectations of the herd-immunity theory are bound to fail in the real world.”

Lawrence Solomon is research director of Consumer Policy Institute.

For the Public Health Service’s four-page prediction that measles would be eliminated in 1967, see here.

For the untold story of measles, see here.

For previous columns in this series on vaccines, see here.

For a response to this column by Sierra Rayne published on June 24, 2014, by American Thinker, see: Clarifying the debate over measles vaccinations, in which Rayne takes issue with several of Mr. Solomon’s statements, particularly in regard to risk factors for children.