From Mpox To Measles: Are We Living In The Age Of Disease Outbreaks?

Discussion about disease outbreaks dominated the biannual meeting of the Strategic Advisory Group of Experts on Immunization (SAGE) – which its chairperson described as  “alarming” as the aim of the group is to ensure early vaccination to prevent outbreaks.

“The outbreak-related recommendations is a sign that normalcy is starting to be living with outbreaks,” warned Dr Hanna Nohynek, chair of SAGE, which advises the World Health Organization (WHO) on immunisation.

“My plea to nations is to give us sufficient resources so that we can run our programmes properly and our surveillance systems properly so that we don’t have to deal with outbreaks but we can actually keep up our good vaccine coverage.” 

Mpox: different epidemiology 

There is a “significant” mpox outbreak in the Democratic Republic of Congo (DRC) that involves Clade I of the disease and is predominantly affecting children.

But this outbreak has “a very different epidemiology” from the multi-country outbreak in 2022, which involved the milder Clade II and was mainly spread through sexual transmission, particularly in men having sex with men, said Dr Kate O’Brien, WHO Director of Immunization, Vaccines and Biologicals.

“It’s really important to understand what the source of the mpox exposure is [in DRC], which is presumably related in part to zoonotic transmission, and potentially transmission then in the household or in the community,” she added.

Children in the DRC are being given mpox vaccines (both on- and off-label, depending on which vaccine is involved), and O’Brien urged the country to conduct evaluations of its performance “which we expect to be very high in settings of community transmission”.

“The vast majority of mpox vaccine data is from high income countries and predominantly in communities where there has been sexual transmission,” she noted.

“We have a lack of research, be it clinical research or epidemiological research, in relation to diseases that are most pressing in low income countries and the issue came up in particular in relation to mpox,” said SAGE’s executive secretary, Dr Joachim Hombach, who is also WHO senior health advisor.

“More research needs to be done and, whenever possible local research because the competencies are there it is just that the resources are not, so that more data is generated to allow for more robust policy and for more robust understanding of the disease epidemiology.”

Measles and misinformation

WHO releases annual measles case and death estimates, and for 2022 there were over nine million cases and 136,000 deaths.

“There are now over 50 countries that have large and disruptive measles outbreaks ongoing during the course of this past calendar year, and that’s about double the number of countries as occurred in 2022,” said O’Brien.

“We warned very much regularly during the course of the [COVD-19] pandemic what the impact would be of the backsliding in immunisation, and we’re seeing that happen now and we do expect that the 2023 numbers will be even worse than the 2022 numbers.”

While there had been an “infodemic” of vaccine-related misinformation during the pandemic, O’Brien stressed that lack of access to vaccines was behind the vast majority of children going unvaccinated. 

“The primary reason for unvaccinated people is really related to the ease of access and the quality of services. But this issue of misinformation, hesitancy and people’s understanding of the value of vaccines is very contributory and in some communities, this is a big contribution to people’s behaviour around vaccines,” she acknowledged.

“The reasons for this misinformation, hesitancy or lack of confidence in vaccines is very, very local so we can’t give global recommendations on exactly what to do,” she added.

However, she urged health authorities to listen to communities, and assure local leaders about the “life-saving nature of vaccines and the safety of vaccines”.

“I want to really emphasise the importance of the process that we have in WHO for pre-qualifying vaccines. Our procedure for pre-qualifying vaccines or issuing an emergency use listing is an assurance to countries that those vaccines are efficacious. They’re safe, and they’re manufactured with quality.”

Polio and Hepatitis E

The wild poliovirus type one is only in circulation in a small geographic area of the border between Afghanistan and Pakistan, but SAGE is concerned about the circulation of vaccine-derived polio type one and type two (VDP2) in a number of African countries.

“Improving routine immunisation coverage is at the heart of getting the eradication goals,” stressed Nohynek.

SAGE is also concerned about Hepatitis E, a liver disease that “can be very severe, especially for pregnant women among whom the case fatality rate can be as high as 25%”, she added. 

“In fragile and conflict-affected and vulnerable settings, it’s really important that pregnant women have access to the vaccine,” said Nohynek.

SAGE has recommended a two-dose schedule, which is off label, instead of a three-dose schedule and additional research on hepatitis E vaccination during pregnancy, in people living with HIV and children under 16.

Image Credits: WHO DRC Office Twitter.