Outbreaks to watch: Vaccine-preventable diseases surge post-pandemic

The COVID-19 pandemic highlighted the importance of immunisation, but it also caused huge disruption to routine vaccination programmes across the globe. As countries focused on fighting the new virus, efforts to eliminate or control older diseases were put on hold.
Between 2019 and 2021, the world saw “the largest sustained decline in childhood vaccinations in approximately 30 years”, according to a joint report from the World Health Organization and UNICEF.
Now, as social distancing measures are relaxed and global travel picks up, old diseases are circulating once again in unvaccinated populations, triggering an uptick in outbreaks even as healthcare systems in many countries come under unprecedented strain.
Polio, diphtheria, measles, and other vaccine-preventable diseases are surging in countries as disparate as Zimbabwe, Pakistan, and the United States. Earlier this week, the WHO launched its 2023 emergency appeal for $2.54 billion, following an “unprecedented” number of intersecting health emergencies.
“The impact of these [COVID-related] disruptions to immunisation services will be felt for decades to come,” WHO chief Tedros Adhanom Ghebreyesus warned last year, adding that “catch-up” immunisation campaigns were urgently required to close vaccine coverage gaps.
The fallout will be most keenly felt in countries that are also dealing with conflict, widespread poverty, climate disasters, or high rates of vaccine hesitancy.
Even before COVID-19, there were concerns that progress on vaccination coverage was stalling: In some Latin American countries, for example, immunisation levels have dropped by over 14% since 2010.
The pandemic then exposed pre-existing gaps in healthcare services, setting back decades of progress towards disease elimination.
Vaccination campaigns have proven to be a cost-effective public health tool, with preventative programmes costing far less than humanitarian responses to disease outbreaks. But the pandemic has made it all too clear that global collaboration is needed for them to succeed.
A first draft of a new global pandemic treaty proposed by the WHO calls for regional vaccine production to forge more equitable access, as well as for the sharing of the technical know-how to allow this to happen. Until then, however, it seems likely that countries around the globe will continue to witness an increase in vaccine-preventable diseases.
Here are some of the outbreaks to watch in 2023:
Measles in African countries, India, and the United States
Measles is one of the most contagious viruses known to humans, causing a high fever and distinctive red rash. It can be fatal for children under five.
The WHO recommends a 95% vaccination rate in order to reach herd immunity. Progress was stalling at around 85% even before the pandemic, but COVID-19 disruptions resulted in a significant decline from that figure. According to a joint report from the WHO and the US Centers for Disease Control and Prevention (CDC), almost 40 million children missed a dose of the measles vaccine in 2021.
The result has been a spike in outbreaks across the globe, with Africa being the worst-hit region. According to the WHO, 20 African countries reported outbreaks between January and March 2022, collectively reporting almost 18,000 cases – a 400% increase compared to the previous year.
Although largely confined to lower-income countries, outbreaks of the virus have also begun to crop up in larger numbers across Europe, as well as in the United States.
The worst of these has been in Zimbabwe, which last year reported over 700 deaths between April and the first week of September. India has also witnessed a spike in cases, with multiple outbreaks across the country leading to the deaths of over 40 children. Both countries have responded with urgent “mop-up” immunisation campaigns, vaccinating all children under five in affected areas regardless of previous vaccination status.
Although largely confined to lower-income countries, outbreaks of the virus have also begun to crop up in larger numbers across Europe, as well as in the United States. In Ohio, for example, an ongoing outbreak leading to the infection of at least 82 children has been blamed on widespread vaccine hesitancy in the wake of the pandemic. The majority of the infected children were unvaccinated.
The return of wild poliovirus in Malawi and Mozambique
The years leading up to the pandemic saw several major achievements in the quest to eradicate polio – a disease that is spread person to person or through contaminated food and water.
Polio, which can cause paralysis and death, largely affects children under five and has no cure, but it is easily preventable through vaccination.
In 2020, Africa was officially declared free from endemic polio, with wild poliovirus confined to Afghanistan and Pakistan. But the pandemic set back progress, temporarily halting immunisation campaigns and leading the global immunisation rate to plummet to 80% in 2021 – the lowest in 14 years.
Globally, vaccine-derived poliovirus cases tripled between 2019 and 2020, leading to the paralysis of over 1,100 children.
As a result, a number of countries saw large outbreaks of vaccine-derived poliovirus, such as Nigeria, which reported 1,027 cases in 2021, according to the WHO. After vaccine-derived poliovirus was discovered in a baby in Sudan, a mass immunisation campaign for children was launched within weeks. Globally, vaccine-derived poliovirus cases tripled between 2019 and 2020, leading to the paralysis of over 1,100 children.
New cases of wild poliovirus have also been detected outside of endemic areas, with Malawi reporting a case of paralysis due to wild poliovirus in February 2022, followed by Mozambique in May – marking a return of wild poliovirus to Africa. The cases triggered a multi-country emergency response, with vaccination campaigns implemented across the affected region.
The ever-present threat of global re-emergence was also highlighted recently after the detection of vaccine-derived poliovirus in sewage systems in Britain and the United States, followed by a US case resulting in paralysis in July 2022.
Diphtheria in Pakistan, Britain, and EU
Diphtheria is a disease caused by a toxin-producing bacteria that can lead to breathing troubles, heart arrhythmia, and occasionally death. It spreads quickly through respiratory droplets in the air, so is particularly liable to cause outbreaks in overcrowded living conditions.
The combined diphtheria, tetanus, and pertussis (DTP3) vaccine – recommended for all children under seven – is seen as a marker for general childhood immunisation coverage.
Widespread vaccination saw a decrease in diphtheria cases of over 90% from 1980 to 2000. However, between 2019 and 2021, the percentage of children who received all three doses fell by 5% to just 81%. In 2021, 25 million children missed a dose, according to the WHO.
This has resulted in an increase in diphtheria, particularly in Europe, where 153 cases were reported across the EU as of November 2022. In Britain, 27 cases were reported in November alone, leading to the death of one man. Most cases have been among asylum seekers, highlighting the dangers of overcrowded and unsanitary conditions in refugee processing centres.
In Pakistan, a diphtheria outbreak caused by inadequate immunisation has been exacerbated by the recent flooding, claiming the lives of at least 45 children. Flood-affected provinces reported around 70 suspected cases in November 2022 alone.
Cholera in Haiti, Malawi, Lebanon, and Syria
The WHO has warned of an “unprecedented” surge in cholera cases, with outbreaks reported in around 30 countries in 2022, including Haiti, Malawi, Lebanon, and neighbouring Syria.
“Not only are we seeing more outbreaks, but these outbreaks are larger and more deadly than the ones we have seen in the past years,” Dr Philippe Barboza, team lead for cholera at the WHO, told UN News.
A complex combination of factors is driving this surge.
Cholera is spread by ingesting contaminated food or water, and can be deadly, particularly for young children or those with pre-existing health problems. The WHO has linked the rise in cases to climate change, which has increased the frequency and severity of droughts, flooding events, and cyclones.
However, essential WASH (water, sanitation, and hygiene) programmes have also been disrupted by the pandemic, and the economic fallout from lockdowns has exacerbated poverty and added pressure to healthcare services that oversee cholera surveillance and immunisation campaigns.
The worst-affected countries each have their own individual drivers too.
“Not only are we seeing more outbreaks, but these outbreaks are larger and more deadly than the ones we have seen in the past years.”
Gang warfare in Haiti has devastated the healthcare system, with some 24,451 suspected cholera cases recorded by 16 January – barely four months after the first cases in three years were discovered.
In Malawi, which had also successfully beaten back cholera in recent years, a slowdown in vaccinations, severe storms, growing urbanisation, and a slow government response has led to nearly 30,000 cases and 990 deaths since the outbreak began in February 2022.
In Lebanon, the fact that cholera returned in October after three decades was seen as a testament to the depth of the country’s financial crisis.
Neighbouring Syria, meanwhile, has seen more than 77,500 suspected cases and 100 deaths as an impoverished population contends with an overstretched health system and inadequate clean water.
Although it’s not 100% effective, cholera is largely preventable through vaccination.
In 2017, a new global strategy was launched by The Global Task Force on Cholera Control, a partnership of more than 50 institutions that aims to reduce cases by 90% by 2030 through vaccination and WASH campaigns.
However, the recent surge in cases has led to a vaccine shortage as stockpiles run short, causing the WHO to temporarily revise recommendations on vaccination to just one dose instead of two, and threatening to further encourage the spread of the disease.

Source: The New Humanitarian