Typhoid Mary and the dangers of vaccine complacency

TL;DR keep wearing that mask

Coronavirus restrictions are set to be lifted completely in England in less than a week’s time. With the number of Covid-19 cases at its highest since January, this counterintuitive move will inevitably lead to a further rise in cases, more deaths and more incidents of the life-limiting morbidity associated with ‘long Covid’.

Much has been written about the British government’s ongoing indifference to keeping its citizens safe. But in the absence of competent, responsible leadership, it’s worth reflecting on the role of the individual, not only to protect others, but to protect the legacy of humanity’s fight against disease.

Vaccines: humanity’s greatest achievement

Vaccines are one of the greatest (if not the greatest) human discoveries. Vaccination programmes are the finest example of global human cooperation. At the start of the twentieth century, life expectancy in the developed world was just 47. By the end, it was 77. Vaccination played an enormous role in this astonishing advancement.

At the beginning of that period, for example, more than 60,000 people in Britain fell ill with diphtheria every year, resulting in about 6,000 deaths. At least two of my infant ancestors were among them. Polio, meanwhile, very nearly killed my grandmother and left her father disabled for life. Smallpox was ravaging the world.

Today, babies, including my own daughter, are vaccinated against diphtheria, polio and four other deadly diseases at a routine trip to the GP. As a result, there was a single recorded death from diphtheria in the UK in 2019. Since its launch in 1988, The Global Polio Eradication Initiative has reduced cases of polio across the world by 99 per cent. We now talk about smallpox, a disease that killed 300 million people in the twentieth century, in the past tense.

These gains are enormous. But they are not to be taken for granted. In 2010, a whooping cough outbreak in California took the lives of ten people, most of them children. Between 2016 and 2019, measles deaths increased by fifty per cent. The eradication of disease is not a given.

A large part of such regression is the result of so-called ‘anti-vax’ movements, peddling misinformation and conspiracy. This is abhorrent, cruel and exploitative and must be tackled as an imperative. But what is also concerning at this point in our history is the potential for simple complacency to become a factor in walking back the gains we have made, particularly in this pandemic.

Our response to Covid-19 thus far has been especially impressive. The gene sequencing of the original virus was achieved within a single day, while the production of several effective vaccines began within months of the first confirmed cases. Almost a billion people worldwide have been fully vaccinated just 18 months after the first lock-down began. Again, these are achievements of cooperation, but our continued success now depends on people recognising their individual power.

‘Typhoid Mary’ – the world’s first known asymptomatic carrier

The case of ‘Typhoid Mary’ is a prime example of how the apparent wellness of a single individual can conceal a devastating vector of disease transmission.

Mary Mallon was born in 1869 in Ireland and emigrated to the United States at the age of 15. There, she became a cook in the kitchens of wealthy New York families. Over a seven year period, several members of those families, as well as other domestic staff, fell ill with typhoid fever. Eventually a pattern emerged with Mary at the heart of it.

Mary Mallon was the first known case of an asymptomatic carrier of disease – and a ‘super-spreader’ to use modern parlance. Although she never exhibited symptoms of typhoid, herself, it is believed that she infected at least 53 people, three of whom died. From this, she acquired the sobriquet ‘Typhoid Mary’.

The story of Mary Mallon is particularly tragic because she was forcibly quarantined for much of her life, obliged to give samples against her will. Germ theory was still not fully understood or supported, and Mary refused to believe that she could be the source of the outbreaks, even up until her death in 1938.

Although Mary’s treatment was highly ethically questionable, it did reveal that a person who does not show symptoms of a disease can still carry and pass on that disease. This theory has been borne out repeatedly in the cases of tuberculosis, HIV and, latterly, Covid-19.

The power of the individual as part of a whole

Mary Mallon’s trail of destruction was utterly unintentional. Today, we know about asymptomatic carriers, how diseases spread and how vaccines work in populations.

No vaccine is one hundred per cent effective. Vaccination programmes work because the proportion of vaccinated people is sufficient to reduce outbreaks, so that populations no longer come into contact with disease in the first place. A successful vaccination programme protects both vaccinated and unvaccinated people. The latter group avoids contracting diphtheria not because they’re lucky or strong, but because the people around them have actively behaved in a way that protects them. Vaccination success depends on the willingness of individuals to cooperate with other individuals in the interest of the community.

Mary Mallon’s case is especially pertinent today because, as with asymptomatic typhoid, it is entirely possible for a person who is double-vaccinated against Covid-19 not only to become infected, but to spread the disease inadvertently.

Half of the British population is now fully vaccinated. At the same time, the more contagious Delta variant (as well as its eager cousins, Eta, Kappa and Lambda) is wreaking havoc despite our efforts. The current raft of vaccines does seem to work against variants but there is no guarantee that they will continue to do so. Vaccination is vital, but it is only part of a puzzle that is built as much on personal responsibility as on scientific progress.

Covid-19 has so far killed at least four million people, including my own grandmother, and has touched the lives of millions more. It will continue to do so unless we acknowledge our own role in the ongoing story of humanity versus disease. As the vaccination roll-out continues, as case rates eventually stabilise or decline, and as more and more restrictions on our everyday behaviour are lifted, it behoves us to remain as vigilant and thoughtful as possible.

Now is as good a time as any to reflect on lessons from the past and proceed in the vein of human cooperation that has brought us to this point. That’s what’s at stake come July 19th.

Weigh in! Will you still be wearing your mask after 19 July? What are your thoughts about the lifting of restrictions in England?