Internet shopping anyone? In 2011, one enterprising mother from Nashville, Tennessee, used her Facebook page to advertise lollipops sucked by her child who was suffering from chickenpox. The declining incidence of chickenpox in the US has created a market for such commodities. Since 1995, a vaccine against the disease has been included in the standard immunisation schedule generated by the Advisory Committee on Immunization Practices (in the UK it is an optional vaccine, offered by the NHS in specific circumstances).

The lollipop idea appeals to parents who prefer not to adhere to the official schedule for fear of overwhelming the child¡¯s immune system, or who eschew vaccination completely in favour of ¡°natural immunity¡±. In the case of chickenpox, such immunity is achieved by contracting the disease; for the more serious illnesses, boosting the immune system through enhanced nutrition is a popular parenting choice. In effect, what these parents rely on is the herd immunity created by all those children who have been vaccinated. Should anyone be tempted to try the lollipop approach, it¡¯s illegal in the US. While the chances of catching chickenpox from a contaminated lollipop are remote, there are risks from other saliva-borne infections.

Risk is one of the operative words central to sociologist Jennifer Reich¡¯s remarkably calm book on current vaccination practices in North America. Risk is what parents, paediatricians and policymakers must evaluate in their roles as caregivers, primary-care doctors and advisers. For those who oppose immunising their children, the statistically very slight risk of damage caused by vaccines outweighs the higher risks of contracting a disease and then suffering severe outcomes. Determining risk has traditionally been the job of experts, but these parents claim that they are the experts on their own children. While they may read up on the subject, they accord their intuitive understanding greater weight than demonstrable, certified medical and scientific knowledge. In our less deferential society, the role of the expert in many fields has been undermined by a new grass-roots self-confidence.

The group of parents Reich interviewed over a 10-year period that has informed this book are the university-educated ubermoms who favour organic food and have a tendency to avoid gluten and dairy products. They are also concerned about what they see as a conspiracy by the pharmaceutical companies who produce vaccines, the doctors who prescribe them and the official bodies that create and endorse the vaccine schedule. They see themselves as sensibly exercising their responsibility to the unique body of each child they bear. This includes finding a paediatrician who will work with them to this end. The doctors Reich interviewed recognise that some vaccination is better than none and that being patronising, bossy or confrontational is not in the best interests of the child or the wider community. It is a stance Reich shares.

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While the doctors cannot afford to lose sight of the well-being of the community, these parents may be deliberately setting themselves apart from it, not just because they are fearful about vaccines but because exercising individual choice has become the most important way to live their lives. Only in years to come will we know just how great a risk these home-grown experts have taken.

Helen Bynum is honorary research associate in the department of anthropology, University College London.

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Calling the Shots: Why Parents Reject Vaccines
By Jennifer A. Reich
New York-University Press, 336pp, ?24.99
ISBN 9781479812790
Published 21 June 2016