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HomeA FocusMonkeypox possibly linked to decrease in smallpox vaccine – global experts

Monkeypox possibly linked to decrease in smallpox vaccine – global experts

Theories are varied regarding the unusual outbreak of monkeypox, a rare tropical disease that appears to be spreading across the globe, with some linking the cause to sexual activity, and other scientists attributing it to the waning effects of smallpox vaccination, notes MedicalBrief.

Cases have been reported across at least a dozen European and North American countries this month. It is the first time the virus has been found in people with no clear connection to Western and Central Africa, BBC News report.

So far, 15 countries have collectively reported more than 145 cases, most of them in Spain (50) and Portugal (34), but none has been reported in South Africa, says the National Institute for Communicable Diseases (NICD).

At this stage, men, aged between 20 and 55, have accounted for more than 70%, of the cases, with most detected through sexual health services. The majority of the cases are mild, and present with lesions on the genitalia or peri-genital areas. Additional symptoms include rash, fever, painful lymph nodes and oral ulcers.

“The implications for South Africa are that the risk of importation of monkeypox is a reality, as lessons learnt from COVID-19 have illustrated that outbreaks in another part of the world can fast become a global concern,” says NICD executive director Prof Adrian Puren.

The Associated Press reports that a leading adviser to the World Health Organisation (WHO) described the unprecedented outbreak in developed countries as “a random event” that might be explained by risky sexual behaviour at two recent mass events in Europe.

In an interview with AP, Dr David Heymann, who formerly headed WHO’s emergencies department, said the leading theory to explain the spread of the disease was sexual transmission among gay and bisexual men at two raves held in Spain and Belgium. Monkeypox has not previously triggered widespread outbreaks beyond Africa, where it is endemic in animals.

From past instances of human-to-human transmission, scientists have learned that the virus spreads through the exchange of large respiratory droplets or via direct contact with bodily fluids, lesions that form during infection, or contaminated items like clothing or bedding.

Monkeypox is not considered a sexually transmitted infection, but it could be passed during sexual encounters, experts said. Many of the recent cases in Europe are among men who have sex with men, and an alert from the US Centres for Disease Control and Prevention (CDC) last Friday suggested that some recent cases started out with lesions around the anus and genitals.

"I'm guessing that sexual transmission will be high on the list of potential culprits," said Dr Grant McFadden, director of the Biodesign Centre for Immunotherapy, Vaccines and Virotherapy at Arizona State University.

However, other scientists are convinced that waning smallpox immunity “established the landscape” for monkeypox resurgence. They said discontinued vaccination campaigns for the now-eradicated disease were possibly related to the resurgence of monkeypox.

Healio reports that the scientists reached this conclusion after systematically reviewing dozens of studies and other documents for data on the evolution of monkeypox epidemiology over the past 50 years, which revealed that cases have been increasing since routine smallpox vaccination ceased.

Interestingly, their findings were published in February, in PLOS Neglected Tropical Diseases, months before the recent outbreaks of cases were reported in Britain, the United States and several other countries.

“Based on initial literature review, we thought there was an increase of cases of monkeypox, which was not systematically reported at that moment,” Dr Bernard Hoet, vice-president of medical strategy at Bavarian Nordic, told Healio, “and thus thought it would be of use to document this formally.”

Hoet and colleagues conducted a systematic review of 48 peer-reviewed studies and 18 grey literature sources, looking primarily at the number of cases of monkeypox, age at presentation, mortality and geographical spread.

Overall, the number of human monkeypox cases has been on the rise since the 1970s, they found, most dramatically in the Democratic Republic of the Congo (DRC). The median age of patients with monkeypox increased from four years in the 1970s to 21 years between 2010 and 2019.

And overall, 8.7% of patients with monkeypox died – 10.6% (95% CI, 8.4%-13.3%) of those infected with the Central African clade of the virus and 3.6% (95% CI, 1.7%-6.8%) infected with the West African clade, which has been implicated in the recent cases.

The researchers noted that smallpox vaccination provides some cross-protection against monkeypox. A licensed vaccine that protects against monkeypox and smallpox – Bavarian Nordic’s Jynneos – was approved by the US Food & Drug Administration (FDA) in 2019 for adults aged 18 years or older in America. The company said in 2020 that the US had ordered millions of doses of the vaccine for the national stockpile.

According to Hoet and colleagues, 21 articles reviewed by the researchers reported smallpox vaccination status. Eleven described outbreaks from 10 different countries that included 49 patients with monkeypox – none of whom was vaccinated.

In the other 10 articles, which reported data from outbreaks in the DRC and US, the proportion of monkeypox cases with a history of prior smallpox vaccination ranged from 4% to 21%. They noted that the highest percentage of vaccinated cases (21%) was found in the US outbreak in 2003 that was linked to imported prairie dogs.

“Monkeypox is not a benign disease,” Hoet said. “This should be taken into account for the preparedness plans of authorities. We have a disease potential which seems to be materialising at the moment for which we have an option. It should raise the attention of health agencies to be prepared.”

Corroborating his evidence of the waning effects of smallpox vaccines was Rodney Rohde, professor of clinical lab science at Texas State University. In an article in The Conversation, Rohde said because monkeypox is closely related to smallpox, the smallpox vaccine can provide protection against infection from both viruses.

“Since smallpox was officially eradicated, however, routine smallpox vaccinations for the US general population were stopped in 1972. Because of this, monkeypox has been appearing increasingly in unvaccinated people.”

He said it was unlikely to cause another pandemic, “but with COVID-19 top of mind, fear of another major outbreak is understandable”. Though rare and usually mild, monkeypox can still potentially cause severe illness, he added.

Evidence suggests that the smallpox vaccine can help prevent monkeypox infections and decrease the severity of the symptoms. One vaccine known as Imvamune or Imvanex is licensed in the US to prevent monkeypox and smallpox.

Vaccination after exposure to the virus may also help decrease chances of severe illness. The CDC currently recommends smallpox vaccination only in people who have been or are likely to be exposed to monkeypox. Immunocompromised people are at high risk.

However, the WHO does not believe the outbreak outside Africa requires mass vaccinations, saying measures like good hygiene and safe sexual behaviour will help control its spread, a senior official said.

Richard Pebody, who leads the high-threat pathogen team at WHO Europe, told Reuters on Monday (23 May) that immediate supplies of vaccines and anti-virals are relatively limited.

On the same day, Germany’s Government said it was assessing options for vaccinations, while Britain has offered them to some healthcare workers.

Most of the confirmed cases have not been linked to travel to Africa, which suggests there may be large amounts of undetected cases, said Pebody. Some health authorities suspect there is some degree of community spread.

“So we’re only seeing … the tip of the iceberg,” he said.

The Joint United Nations Programme on HIV/Aids (UNAIDS) has expressed
concern that because a significant portion of the recently reported monkeypox cases had been identified among gay, bisexual and other men who have sex with men, “some media reporting and commentary was reinforcing homophobic and racist stereotypes”.

According to the WHO, available evidence suggests that those who are most at risk are those who have had close physical contact with someone with monkeypox, and that risk is not limited, in any way, to men who have sex with men.

Meanwhile, the Foreign Press Association, Africa (FPAA) has asked editors to censure their staff from using images of Africans, people of African descent, or people living in Africa to cover outbreaks of the disease. Business Insider reports that FPAA has condemned media outlets for using images of black people in their coverage of monkeypox.

UNAIDS urged media outlets, governments, and communities to respond with a rights-based, evidence-based approach that avoids stigma.

Study details

The changing epidemiology of human monkeypox—A potential threat? A systematic review

Eveline M. Bunge, Bernard Hoet, Liddy Chen, Florian Lienert, Heinz Weidenthaler, Lorraine R. Baer, Robert Steffen.

Published in PLOS Neglected Tropical Diseases on 11 February 2022

Monkeypox, a zoonotic disease caused by an orthopoxvirus, results in a smallpox-like disease in humans. Since monkeypox in humans was initially diagnosed in 1970 in the Democratic Republic of the Congo (DRC), it has spread to other regions of Africa (primarily West and Central), and cases outside Africa have emerged in recent years. We conducted a systematic review of peer-reviewed and grey literature on how monkeypox epidemiology has evolved, with particular emphasis on the number of confirmed, probable, and/or possible cases, age at presentation, mortality, and geographical spread. The review is registered with PROSPERO (CRD42020208269). We identified 48 peer-reviewed articles and 18 grey literature sources for data extraction. The number of human monkeypox cases has been on the rise since the 1970s, with the most dramatic increases occurring in the DRC. The median age at presentation has increased from 4 (1970s) to 21 years (2010–2019). There was an overall case fatality rate of 8.7%, with a significant difference between clades—Central African 10.6% (95% CI: 8.4%– 13.3%) vs. West African 3.6% (95% CI: 1.7%– 6.8%). Since 2003, import- and travel-related spread outside of Africa has occasionally resulted in outbreaks. Interactions/activities with infected animals or individuals are risk behaviors associated with acquiring monkeypox.

Our review shows an escalation of monkeypox cases, especially in the highly endemic DRC, a spread to other countries, and a growing median age from young children to young adults. These findings may be related to the cessation of smallpox vaccination, which provided some cross-protection against monkeypox, leading to increased human-to-human transmission. The appearance of outbreaks beyond Africa highlights the global relevance of the disease. Increased surveillance and detection of monkeypox cases are essential tools for understanding the continuously changing epidemiology of this resurging disease.


Healio article –Waning smallpox immunity ‘established the landscape’ for monkeypox resurgence (Open access)


PLOS Neglected Tropical Diseases article – The changing epidemiology of human monkeypox—A potential threat? A systematic review (Open access)


UN article – Monkeypox: UNAIDS ‘concerned’ about stigmatizing language against LGTBI people


Business Insider article –African journalists condemn media outlets for using images of Black people in coverage of US, UK monkeypox (Open access)


NICD article – Situation update – monkeypox (Open access)


The Associated Press article – Expert: Monkeypox likely spread by sex at 2 raves in Europe (Open access)


The Conversation article – What is monkeypox? A microbiologist explains what’s known about this smallpox cousin (Creative Commons Licence)


Reuters article – WHO says no urgent need for mass monkeypox vaccinations (Open access)


See more from MedicalBrief archives:


CDC expresses concern over monkeypox outbreak in UK


UK reports first case of monkeypox, probably from Nigeria





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