Fear of Vaccines

The term also covers accepting vaccines while remaining uncertain about them, and using some but not others. The scientific consensus that vaccines are generally safe and effective is overwhelming, adverse effects are occasionally observed as with any treatment, and the outcome of the hesitancy is outbreaks and deaths from diseases that were preventable. The World Health Organization lists it among the top ten global health threats.

What feeds vaccine hesitancy

Hesitancy is complex and context-specific, varying by time, by place and by which vaccine is in question. The contributing factors named are:

• a lack of scientific understanding of how vaccines are made or work
• fear of needles
• distrust of public authorities, healthcare providers included
• complacency, meaning the person sees no need or no value in it
• convenience, meaning whether the vaccine is easy to get

It is older than the vocabulary. Hesitancy predates the coining of the words vaccine and vaccination by nearly eighty years, having existed since the invention of the procedure. Myth, conspiracy theory and deliberate disinformation, put out by the anti-vaccination movement and by doctors on its fringe, keep a public argument running over medical, ethical and legal questions. Inside mainstream medicine and science that argument does not exist: the benefits are not in dispute there.

Why a vaccine looks riskier as the disease disappears

Vaccines create the conditions for doubting them. Because they are given to healthy people, they are held to a higher safety standard than other interventions, and serious complications are extremely rare and far less common than the risks of the diseases prevented. But as an immunisation programme succeeds, public attention shifts from the risk of the disease to the risk of the vaccine.

The mechanism is a failure of heuristic reasoning. Once a disease such as Haemophilus influenzae B becomes rare, people lose familiarity with how serious it was, and the perceived danger falls, and with it the perceived benefit of immunisation. The reverse failure also happens: influenza remains so common that hesitant people read it as non-threatening, despite clear evidence to the contrary. Omission and disconfirmation biases do the rest.

How a vaccine scare runs its course

Safety concerns tend to run through the same sequence.

1. Someone proposes that an illness whose numbers are climbing, or whose cause nobody knows, is being produced by a vaccine.
2. The study making the claim, and the ones the same group publish afterwards, are methodologically weak, and what they usually amount to is a case series with poor controls or none.
3. A premature announcement lands, resonating with people who have the condition and understating the harm of forgoing vaccination for those the vaccine would protect.
4. Other groups attempt replication and fail.
5. Rebuilding confidence takes years.

The alleged effects share a profile: unknown origin, rising incidence, some biological plausibility, occurrence close in time to vaccination, and a dreaded outcome.

What vaccines are accused of containing and causing

Thiomersal, an antifungal preservative used in small amounts in some multi-dose vaccines to prevent contamination, was removed from common US and European vaccines on the precautionary principle after a 1999 request from the CDC and the American Academy of Pediatrics. That removal itself sparked the concern that it had caused autism, which is considered disproven, because autism incidence continued rising steadily after the removal. A vaccine containing 0.01 per cent thiomersal carries about 25 micrograms of mercury per half-millilitre dose, roughly what is in a three-ounce can of tuna.

Formaldehyde does a different job, going in at low concentration to kill off the viruses and neutralise the bacterial toxins, and whatever residue it leaves sits well under any level that would matter. The human body produces it continuously and holds 50 to 70 times the largest amount present in any vaccine.

The MMR case is the most consequential. Andrew Wakefield published twelve case histories in The Lancet in 1998. Most of the children had autism spectrum disorders, and in each the onset had followed shortly after they were vaccinated. At the press conference he went further than his own paper did, proposing that splitting the vaccine into three separate doses would be safer. He had received funding from litigants against vaccine manufacturers without informing colleagues or medical authorities, and reportedly stood to earn up to 43 million dollars a year selling diagnostic kits. UK vaccination rates fell to 80 per cent in the following years. Ten of the thirteen coauthors retracted the autism interpretation in 2004; The Lancet retracted the paper entirely in 2010; Wakefield was struck off the UK medical register for deliberate falsification. The British Medical Journal described the work as an elaborate fraud that put hundreds of thousands of children at risk and diverted money and effort away from research into what actually causes autism.