Understanding the spread of infectious disease at a time of climate change and political upheaval
must be a priority to ensure the health of migrants
Smallpox was once a highly infectious deadly disease endemic around the world, killing around 300 million people globally in the 20th Century alone.
Thanks to a world vaccination programme the World Health Organisation officially declared smallpox eradicated in 1980.
Polio was a huge public health issues in the late 19th Century with major epidemics in Europe and the US. A breakthrough came in 1952 when Jonas Salk developed the first effective vaccine against polio. This was followed by Albert Sabin’s easily administered oral vaccine in 1961, which led to global mass vaccination programmes. A once debilitating disease causing muscle weakness and paralysis has now become rare.
Migration is driving demographic change in Europe and challenging the ability of vaccination programmes to curb disease. Over the last two decades an estimated 30 million migrants born outside of Europe arrived – predominantly from Asia, Africa, and the Middle East.
The 2018 Lancet Commission on Migration and Health highlighted that migrants to high income countries have lower mortality rates than host populations for non-infectious conditions including heart disease, cancer, and diabetes, but face a two-fold increased mortality risk for infectious diseases, with risks for mortality from HIV and tuberculosis even higher. Few studies have focused on the most vulnerable migrant groups, such as asylum seekers, refugees, and undocumented migrants. In addition to increased mortality from infectious diseases, data suggests that migrants might present late and have worse outcomes, which could lead to increased transmission among migrant communities.
The United Nations’ 2030 Sustainable Development Goals call on member states to ensure health promotion in relation to prevention, treatment, rehabilitation, and palliative care. Many migrants have limited access to these services due to
vast and sudden movements from one region to another, such as the recent exodus from Ukraine, leaving individuals especially vulnerable.
Some migrants in Europe are disproportionately affected by infections including tuberculosis, HIV, and viral hepatitis B and C. The Covid-19 pandemic highlighted the increased vulnerability of migrants with evidence showing higher risk of infection, possibly higher mortality risk, as well as greater hardship from public health protection measures, such as school and workplace closures, than non-migrants.
A review in The Lancet (2022) suggests that while pan-European programmes are in place to tackle tuberculosis, HIV, viral hepatitis and vaccine preventable diseases, migrant health outcomes have not necessarily been prioritised, undermining progress towards health targets for infectious disease control, and vaccination uptake.
Before the Covid-19 pandemic, migrants to Europe comprised a third of all tuberculosis cases in the region in 2019. Reactivation of latent tuberculosis infection among migrants is an important factor in incidence of tuberculosis cases in Europe. Almost half (44 per cent) of people diagnosed with HIV in Europe in 2019 were migrants. Data on hepatitis B and C virus prevalence is more limited, but it is strongly affected by migrants from the east Mediterranean region, south and southeast Asia, eastern Europe, Latin American, and sub-Saharan Africa.
Migrants are also likely to be under-immunised and face greater disease burden, disability and death from vaccine preventable diseases than existing populations within host countries. This is aggravated by incomplete vaccination histories. Unaccompanied minors have particularly low vaccination coverage, possibly related to constant movement and disruption in their country of origin.
Migrant healthcare screening and vaccination programmes vary between European countries. As vaccine coverage falls below herd immunity threshold, migrants and the wider community become increasingly vulnerable to infection.
This was recently exemplified by an outbreak of diphtheria in an asylum centre in Manston, Ramsgate in the UK. Before the advent of vaccination against diphtheria in the UK in 1942, cases of this dreaded disease numbered around 60,000 per year, with 4,000 deaths. Diphtheria is mainly caused by Corynebacterium diphtheria, which produces a toxin that can be transmitted by respiratory droplets and close contact. The toxin rapidly kills cells, and those cells form a greyish-black pseudo membrane that coats the tonsils, throat, and nose, making breathing difficult. Known as the ‘strangling angel’ of children in Victorian times, diphtheria is now so rare that the small number of cases that surfaced in the centre made headline news. According to legal action, started by the charity Detention Action, on behalf of the detained immigrant women, overcrowding and poor sanitation at Manston led to deteriorating health conditions resulting in outbreaks of infectious diseases including diphtheria.
Serious infectious disease outbreaks in migrant communities are not new. A systematic review of outbreaks of vaccine preventable diseases, involving migrants residing in the EU or Economic European Area (EEA) and published in The Lancet (2021), identified 47 vaccine preventable outbreaks across 13 countries. Most outbreaks involving migrants were of measles (24 – 6,496 cases) followed by varicella (11 – 505 cases), hepatitis A (7 – 1,356 cases), rubella (3 – 487 cases) and mumps (2 – 293 cases).
The authors concluded that migrants are vulnerable to vaccine preventable disease outbreaks, with adult and child refugees residing in congregated settings, such as shelters or temporary camps, particularly at risk, and vulnerability to infectious disease varies depending on country of origin.
Although many European countries have guidelines on infection testing and vaccination, the authors of The Lancet review state that there is a “limited focus on migrants … and there is a clear disconnect between recommendations and implementation”.
Migrant healthcare screening has moved from poorly functioning port of arrival screening to a mix of pre-entry screening and community-based detection and vaccine catch-up programmes in countries of settlement. What is needed is a system that maximises testing uptake with linkage to care and treatment uptake and completion – all notoriously challenging in a population that is frequently on the move.
Similar problems exist for vaccination programmes. The Lancet review states that vaccination within migrant communities is suboptimal with only a quarter of European countries having vaccination policies in place specifically for migrants. Few programmes target older (those older than 45 years) migrants who have missed their childhood vaccinations due to war and other disruptions to healthcare systems in their countries of origin. Undocumented migrants are at particular risk of missing prenatal screening checks and postnatal infant immunisation programmes.
Designing comprehensive migrant screening and vaccination programmes is complex and costly. Multiple barriers exist including: Clarity around delivery of culturally appropriate screening and vaccination programmes; who has responsibility for vaccinating migrants; which groups should be targeted; and when and where immunisations should be delivered.
This issue is not going to go away. What we do know is that migration is only likely to increase in coming years, aggravated by accelerating climate change. The United Nations International Organisation for Migration estimates as many as one billion environmental migrants in the next 30 years.
Understanding the emergence and spread of infectious disease during a time of rapid climate change and political upheavals must be a priority if we are to ensure the health of migrants as well as minimising infectious disease risks in host countries.
Evidence-based screening systems and vaccination programmes for migrant communities must be prioritised and resourced to ensure that implementation is culturally appropriate, timely, and comprehensive.
Dr Catherine Conlon, Senior Medical Officer with the HSE, and former Director of Human Health and Nutrition at safefood
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