What human smallpox eradication can teach against monkeypox

A little over four decades ago, something unprecedented in the history of humanity occurred: a human infectious disease stopped circulating in the world. In the year 1980, smallpox was considered eradicated.

It was one of the most devastating diseases that ever existed. Almost one in three people infected with smallpox died. In the 20th century alone, it killed an estimated 300 million people worldwide — that is, 4 million a year.

Now, this path between devastation and eradication brings teachings at a time when a virus from the same family, that of monkeypox, is advancing in an unusual way through countries on all continents, in a process that is still being understood by scientists.

And in Brazil, which was one of the last countries in the world to eliminate smallpox, in the 1970s, the fight against the disease created the basis for the national vaccination program we know today, explains Tania Maria Fernandes, a graduate professor in History of Health Sciences at Casa de Oswaldo Cruz/Fiocruz.

Mark on the arm until 1971

Here, the last cases of smallpox were recorded in 1971, in the northern region of the city of Rio de Janeiro.

At that time, there were already isolated cases of the disease, because since the previous decade the country had been promoting mass vaccination campaigns.

According to Tania Fernandes, vaccination initially covered children from six years old to adults. Then, babies under one year old were also vaccinated.

Those born until 1971 —the last year of vaccination in the country— possibly have a vaccination certificate from the time or a mark on their left arm or leg. This is important because this demographic group may still have some form of immunity that is now in effect against monkeypox (more on the disease below).

At the time, large popular parties were held in city squares across the country to attract public and immunize anyone who showed up, says Fernandes. There were also vaccinations at health posts and campaigns in schools to immunize children.

“Everyone, from zero to one hundred years old, was vaccinated”, details the historian.

In 1962, Brazil created a federal public agency specifically focused on smallpox control, named four years after the Smallpox Eradication Campaign (CEV) and charged with centralizing actions against the disease and monitoring its progress — as part of a global initiative of the World Health Organization (WHO) against smallpox.

“In the period from 1966 to 1971, the CEV coordinated the organization and execution of mass vaccination campaigns in all Brazilian municipalities and cooperated with the state health departments in the structuring of epidemiological surveillance units”, according to Fiocruz’s historical collection.

This surveillance had to report and investigate suspected smallpox cases throughout the country and trace possible chains of contagion. From this, the technique called blocking vaccination was performed: people close to the infected patient were immunized to interrupt the chain of transmission.

Proof of vaccination is also now required when enrolling children in school, explains Fernandes.

“These logics made it possible to create the National Immunization Program (PNI)”, which continues to this day in the Brazilian Unified Health System, says Fernandes.

“The same model was then applied against measles, and the national epidemiological surveillance program was created, which centralizes the notification of notifiable diseases —diseases are notified and cataloged and that is why we have access to case numbers, vaccination and deaths” from so many diseases in Brazil, she adds.

This set of factors led to zero smallpox cases in Brazil still in 1971. Two years later, Brazil was certified by the WHO as free from the disease.

Once that was done, details Tania Fernandes, Brazil ended up exporting professionals who had participated in the Brazilian vaccination campaign to implement similar programs in countries that were still fighting smallpox in Asia and Africa, such as Bangladesh, Ethiopia and Somalia.

The eradication in the world

The last known case of smallpox in the world was recorded in Somalia itself, in 1977. Three years later, the WHO declared the disease eradicated — a unique case to date in world history.

“It is the first and only human disease eradicated on a global scale, thanks to the cooperation of countries”, says the WHO. “This remains one of the most remarkable and profound public health successes in history.”

This success is not easy to replicate in other epidemics — for example, that of Covid-19 — because the diseases have very different characteristics from each other, explains Tania Fernandes.

The “advantage” of fighting smallpox (and now monkeypox) is that the patients are symptomatic —they have very particular lesions and blisters on the skin, which make it easier to identify the disease.

In addition, viruses from the pox family, to which smallpox and monkeys belong, are considered stable, meaning they do not undergo many mutations. Therefore, immunization is usually long-term for those who have been infected or vaccinated.

Sars-CoV-2, the covid-19 virus, is quite different: it is often transmitted asymptomatically, so it goes unnoticed in many people.

And it is an RNA molecule virus, which usually undergoes many mutations — and some of them can evade the immunization of the human body and, in some cases, that of vaccines.

So, like measles, for example, Covid-19 is more difficult to eradicate completely — and public health strategies for these and other diseases end up serving more for control than for complete eradication.

From Vaccine Uprising to Monkey Smallpox

It is worth noting that the history of smallpox is very old — what we have told above were only its final chapters.

The WHO estimates that the virus is more than 3,000 years old, and its vaccine was created in 1796 by the English physician Edward Jenner.

Outbreaks, however, continued throughout the 19th and 20th century.

In Brazil, a historic landmark was the Vaccine Revolt, in 1904, when the country was experiencing a particularly virulent outbreak of the disease. In Rio de Janeiro alone, the country’s capital, 3,500 people would die from the disease that year, according to Fiocruz’s archives.

Jenner’s vaccine already existed here, but its mandatory nature was not rigorously implemented. Until Oswaldo Cruz proposed submitting a bill to Congress to reinforce the mandatory campaign.

This generated a strong reaction among various sectors of society—among other reasons, the (unfounded) fear that the vaccine would spread the disease, and the social discomfort with the fact that married women would show their arm or leg in public to be vaccinated. .

In November 1904, thousands of people took to the streets of Rio to protest, in an insurrection that ended up trying to overthrow the federal government itself and was violently repressed.

In the following decades, vaccination advanced with ups and downs in Brazil and in the world, until the successful global campaign took place in the 1960s.

After world eradication, the smallpox virus was still stored in laboratories — and fears always circulated that it could be used as a biological weapon against younger populations that were no longer being vaccinated.

Therefore, the WHO and some countries maintained stocks of the first-generation vaccine against smallpox. And now, given the recent advance of monkeypox—which until this year was rarely seen outside of West and Central African countries—immunizer factories are already being set up to produce vaccines for these two types of viruses.

The human smallpox vaccine is considered to be highly effective —85%— against monkeypox precisely because the viruses are similar and stable, with little chance of mutation.

Another important point is that monkeypox is considered a much milder disease than human smallpox. Its mortality rate is estimated between 1% and 10%, depending on the strain of the virus and the type of patient (younger children and those with compromised immune systems are at greater risk), against a mortality historically of 30% for smallpox.

“The smallpox virus was very dangerous, it killed a lot, (…) and it was very easy to get contaminated”, says Fernandes.

But, with all the devastation it caused, its control ended up providing a useful learning experience in the face of monkeypox: we already know more about the characteristics of the disease and the virus that causes it, and we have also created more robust structures to face it. , with vaccination and monitoring of cases, in the world and in Brazil.

“Certainly the process of eradicating smallpox and then (fighting) measles gave shape to the systems of notification and control of diseases and the immunization program in Brazil”, says Tania Fernandes.

In addition, “there was a very effective vaccine, mandatory, which had a reasonable acceptance in Brazil. It is important to record this: the country has (until today) a very serious vaccination culture”, says the historian.