Smallpox, as one researcher has emphasised, “was eradicated solely through vaccination”. Today, this achievement feels particularly encouraging and seems ready for a reboot as governments worldwide tell the public that the COVID vaccine will soon end the pandemic and return life to normal.
Worldwide, advance reviews are flooding in. Vaccines are a “light at the end of the tunnel”, our ticket to “normality”. They have brought a “real end” into sight. From New York governor Andrew Cuomo came the inevitable military analogy: the vaccine was no less than “the weapon that is going to win the war”.
The current vaccination campaigns are not attempting to eradicate SARS-CoV-2, the virus that causes COVID. But, based on the history of smallpox vaccination, even the much lower bar of herd immunity will be difficult to clear if we pin so much of our hope on vaccination.
Although the eradication of smallpox is often held up as proof of the definitive success of vaccines, it should not be forgotten that smallpox raged for centuries before it was finally brought to an end. One of the first steps towards eradication took place in 1796 when, as the somewhat apocryphal story goes, Edward Jenner injected pus extracted from a dairymaid’s cowpox lesion into the arm of his gardener’s eight-year-old son.
The following 150 years were marked by concern about the vaccine’s efficacy, safety and side-effects. As late as 1963, British doctors were still alarmed by the slow uptake of routine smallpox vaccination, warning that this “indifference” would require a “vast programme of re-education”.
Hesitancy was not the only problem. Well into the 20th century, vaccines were unequally distributed around the globe, and periodic outbreaks ensured that smallpox remained endemic in much of the world, particularly in developing countries.
By 1967, when the WHO launched the ten-year intensified smallpox eradication programme, four other eradication efforts (hookworm, yellow fever, yaws and malaria) had already failed, and many involved in such programmes had become sceptical about eradication as a goal at all.
Indeed, the 1966 director general of the WHO, Marcelino Candau, believed that disease eradication was simply not possible.
What they had come to realise was that vaccines alone are not enough to contain or eradicate a disease. Instead, it would be essential to combine technological developments – such as the introduction of heat-stable freeze-dried vaccines and the bifurcated (two-pronged) needle – with efforts such as surveillance, case finding, contact tracing, ring vaccination (controlling an outbreak by vaccinating a ring of people around each infected individual), and communication campaigns to find, track and inform affected people.
This sort of programme would encounter various challenges from funding to political strife to cultural practices and norms. It would also cost a whopping 20% of the WHO’s budget and take a decade of intensive labour – and come at the expense of other, more basic healthcare interventions. But eventually it succeeded. Smallpox, outside of the lab at least, was gone.