Ness Investigators/ Nicaise Ndembi, Deputy Director General of the Inaugural International Vaccine Institute (IVI) Regional Africa Office, says humanity’s triumph over smallpox has unintentionally created a new global health risk.
Speaking to the News Agency of Nigeria (NAN) on Sunday in Abuja, Ndembi, who is also Head of Mission, IVI Rwanda, said that the eradication of smallpox left billions of people vulnerable to related viral threats such as Mpox.
He described the recent back-to-back mpox epidemics as a direct consequence of the ‘lost shield’ humanity once had against orthopoxviruses.
“Smallpox eradication was a monumental success, but it came at a cost.
“We stopped vaccinating, and in doing so, dismantled the buffer that once protected humanity from related viruses.
“The Mpox outbreaks are a wake-up call,” he said.
According to him, nearly 50 years after the end of mass smallpox vaccination, up to 70 per cent of the world’s population is now immunologically naïve, with little to no protection against orthopoxviruses, the viral family that includes smallpox and mpox.
He cited a pivotal study by Rimoin et al. (2010), which showed that historic smallpox vaccination was 80.7 per cent effective at preventing mpox, with vaccinated individuals having a 5.2-fold lower risk of infection.
However, he said that as vaccination coverage declined over the decades, this protective buffer has eroded.
“A foundational study published in PNAS and titled Major increase in human monkeypox incidence 30 years after smallpox vaccination campaigns ceased in the Democratic Republic of Congo provided early warning signs.
“It documented a dramatic surge in Mpox cases in the DRC, directly linked to waning smallpox vaccine-induced immunity,” he said.
He said that the threat is no longer limited to Central Africa.
“What was once a localised challenge in the DRC has now become a global vulnerability,” he stated.
He urged world leaders to consider equitable, science-driven strategies to rebuild population-level protection.
He called for urgent investment in next-generation vaccines, improved surveillance systems, and international cooperation to restore immunity against poxviruses before mpox and other related viruses evolve into greater global health threats.
NAN reports that smallpox, caused by the variola virus (an orthopoxvirus). It was one of the deadliest diseases in human history, killing about 3 in 10 people who contracted it.
Symptoms included high fever, fatigue, and a characteristic rash that turned into pus-filled sores. After a global vaccination campaign led by the WHO, smallpox was officially eradicated in 1980, making it the first human disease ever wiped out.
Because of eradication, routine smallpox vaccination stopped worldwide in the late 1970s.
Meanwhile, Mpox (formerly called Monkeypox) is caused by the mpox virus, also a member of the orthopoxvirus family (closely related to smallpox). It is less deadly than smallpox, but can still cause severe illness.
Symptoms include fever, headache, swollen lymph nodes, and a rash that looks similar to smallpox but is usually milder.
Mpox spreads through close contact with an infected person, animal, or contaminated materials.
In recent years, Mpox outbreaks have increased worldwide, partly because population-level immunity from smallpox vaccination has waned.
Meanwhile, Smallpox is eradicated but left the world unprotected; Mpox is filling that gap as the new global orthopoxvirus threat.
NAN
