By Invitation

Herd immunity and how health choices affect those around you

Those who refuse to have their children vaccinated bring harm to their community

In the midst of World War II, the film industry in Hollywood started a nightclub called the Hollywood Canteen, which offered free food and entertainment to American servicemen and women. It was staffed entirely by volunteers from the entertainment industry, including the big stars of that time - one of whom was film and stage actress Gene Tierney.

Tierney, who was then pregnant, came down with rubella following her only appearance at the Hollywood Canteen and she subsequently gave birth to a baby girl who was brain damaged, severely underweight, and both deaf and blind. Years later, Tierney met a woman who was a big fan of hers, who professed that she had gone to the club that night to meet her despite being in quarantine with rubella. "Everyone told me I shouldn't go," she said, "but I just had to go. You were my favourite."

In children and adults, rubella (or German measles) is usually a relatively mild and self-limited infection - but its effects on a foetus are devastating, especially if the infection occurs early in pregnancy. If it does not result in miscarriage, it can result - as in Tierney's daughter - in congenital rubella syndrome where the baby is born with a slew of problems, including eye defects, deafness, heart deformities, microcephaly and intellectual disability.

Congenital rubella syndrome is now rare owing to the perinatal screening of women for their immunity against rubella and the successful immunisation programme in Singapore.

The rubella inoculation is given together with those for measles and mumps in the form of the measles, mumps, rubella (MMR) vaccine, and because measles vaccination is mandated under the Infectious Diseases Act, the vaccination rate for these three diseases has been kept high.


The widespread adoption of vaccinations has been one of the greatest public health measures and has saved countless millions of lives round the world. Its success - which has both protected most people in developed countries from these terrible infectious diseases and made them innocent of their ravages - has shifted the fears instead to the risks of the vaccinations. While there are risks and side effects to these vaccinations, these are minimal and minor; the vaccinations today are never as dangerous or as risky as contracting the infections that these vaccinations seek to prevent.


Admittedly, there is something scary and menacing about the act of inoculation, with the loaded syringe making its inexorable way towards our bodies. And when the "needle breaks the skin", writes Eula Biss in her long essay On Immunity, it is "a sight so profound that it causes some people to faint, and a foreign substance is injected directly into the flesh", and "the metaphors we find in this gesture are overwhelmingly fearful, and almost always suggest violation, corruption and pollution". The terror is of this "foreign substance" causing havoc inside us - either by overwhelming our immune defences or poisoning us with some toxins, and causing all sorts of imagined conditions.

Much of these fears about vaccination started in 1998 when British doctor Andrew Wakefield published a paper in prestigious medical journal The Lancet that claimed a causal link between the symptoms of autism and the MMR vaccine. At a press conference, he said there had been an increase in the incidence of autism following the introduction of the MMR vaccine.

The media storm that followed fanned waves of panic among parents and led to a precipitous drop in vaccination rates in Britain and the United States. Consequently, there were outbreaks of measles and mumps that left tens of thousands of children stricken across the US, Canada and Europe, and resulted in deaths.

Most people tend to put a great deal more weight on their own experiences or on anecdotes drawn from the lives of others, and/or bits and pieces gleaned from the Internet... Debunking and rebutting with scientific facts do not work as research has shown; it actually hardens the conviction of believers and spreads familiarity with these falsehoods and misconceptions.

Mr Wakefield's study was subsequently found to be flawed and fraudulent. His medical licence was revoked and the article was retracted by The Lancet - but the damage was done. Despite many other studies that found no link between the MMR vaccine and autism, the animus towards the vaccine persists to this day, particularly in the US where there is an active and vociferous anti-vaccine movement with its entrenched culture of paranoia that sees a conspiracy between the medical establishment, the pharmaceutical companies that make these vaccines, and the government.

President Donald Trump had waded into the fray during his election campaign, expressing and tweeting - either out of political expediency or real conviction - his belief about vaccinations' ties to autism. To have the president of the world's most powerful country - most powerful in science as well - espousing such "alternative facts" is to legitimatise these fringe conspiracy theories.

Most people tend to put a great deal more weight on their own experiences or on anecdotes drawn from the lives of others, and/or bits and pieces gleaned from the Internet. The danger here is the likelihood of confusing association of two events with causality.

"My science is named Evan and he's at home. That's my science," declared American actress and strident anti-vaccine activist Jenny McCarthy, whose son Evan has autism that she has linked to his vaccination. She has also proudly declared that she acquired her knowledge about vaccination from the "University of Google".

Debunking and rebutting with scientific facts do not work as research has shown; it actually hardens the conviction of believers and spreads familiarity with these falsehoods and misconceptions. And such beliefs can have bad consequences.


Vaccination protects not just the individual but also the community. Epidemics happen when a pathogen spreads from a person to many others in a multiplying manner; but when enough people in that community are vaccinated against that disease, those unvaccinated people are generally protected as the pathogen will have problems moving from one host to another, and will cease to spread.

This is the scientific concept of herd immunity that speaks of our interdependency when we live in a community and where our physical health (and lives) depend on the choices that others make. And to attain herd immunity in a population, public health experts say there must be at least a 95 per cent vaccination rate.

Although there is no overt anti-vaccination movement here, there are parents who do not get their children vaccinated: The number of measles cases in Singapore nearly tripled last year compared with the previous year, and 14 out of the 50 cases occurred in children who had missed their MMR vaccination.

Parents who do not want their children vaccinated are probably wanting to play it safe, but ironically they are putting their children at risk of being infected with measles - a disease that is so contagious that 90 per cent of those who have been exposed and are not immune will be infected, and this can lead to encephalitis and death. But it is not just measles alone that should be of concern; there is also mumps, which can cause deafness and even death, albeit rarely; and there is rubella.

While most pregnant women today ought to be immune against rubella, there are some who would not be able to mount that response or where the resistance would go down with time - rendering them and their babies inside them vulnerable.

The only thing to do is to hope they do not get infected - by staying away from anyone who might have rubella - but with half of people with rubella having no symptoms and hence not even knowing that they are infectious, that can be difficult.

From a particular perspective, it is not right that parents who refuse to have their children vaccinated should make such potentially harmful decisions for their children, who do not have the agency to decide for themselves; and it is also not right that they are putting other children, other vulnerable adults and unborn babies in harm's way.

There is a literary coda to Tierney's tragic twist of fate: Agatha Christie was to later use this in her detective novel, The Mirror Crack'd From Side To Side, where she had a pregnant American film actress being unwittingly infected with rubella by a woman seeking her autograph, and which led to the birth of a disabled child. When the actress found this out years later, she murdered the woman with a daiquiri spiked with poison.

Tierney did not kill her fan but she was severely depressed for many years.

  • The writer is vice-chairman of the medical board (research) at the Institute of Mental Health.
A version of this article appeared in the print edition of The Straits Times on April 29, 2017, with the headline 'Herd immunity and how health choices affect those around you'. Print Edition | Subscribe