The measles vaccine was invented in the 1960s, and by the 1980s its use was widespread. Decades later, however, the disease persists. In 2015, nearly 200,000 measles cases were registered worldwide and 73,844 children under the age of four died from this avoidable evil. The World Health Organization (WHO) has postponed its eradication target and now plans to achieve measles elimination in at least five of the six WHO regions by 2020. Based on the current immunization rates, this will be no easy task.

In 2015, 105 of the 187 countries analysed by the WHO (out of the 196 existing in total) had not achieved the immunization rate necessary to create a shield capable of curbing measles transmission, the so-called herd immunity. That is to say, over half of the countries in the world have not given the first dose of the vaccination against this disease to at least 95% of children of the age to be vaccinated, the required percentage for the shield to be effective. Measles is such a highly contagious illness that it requires a very high immunization rate amongst a population to create this protective barrier. Vaccinating 95% of the population not only avoids measles spreading when there is an outbreak but also, by curbing transmission, protects those who cannot be vaccinated, such as babies who are not yet old enough or people with weakened immune systems, allergic to vaccine components or other health problems. Thanks to herd immunity, these groups are also protected. An outbreak which occurred in Romania in 2016, killing several babies younger than one year (who had not reached the age of vaccination), demonstrated the tragic consequences of not reaching the necessary immunization rates.

The pattern is clear (although there are exceptions): the average immunization rate in low-income countries (as defined by the World Bank) is under 83%, while in high-income countries the average rate is almost 95%. But contagion is not a local phenomenon, nor even regional, nor much less determined by level of income. The contagion of such an elusive disease does not stop at any border, it is a global problem. And the planet’s shield against measles, in that very first dose, is of 85%.

The figures -sources and methodology- worsen if we take into account that these percentages, which are just estimations, pertain to the initial dose of the vaccine, that is usually given at one year of age (in the majority of cases, in combination with other vaccines such as those for mumps and rubella, the so-called MMR vaccine) and that two doses are required for protection to be effective. The figures for second doses are worse still. Only 50 of the 143 countries analysed by the WHO reached a second dose immunization rate of 95%.

Remarkable examples include Malawi, with an immunization rate of 85% for the first dose and just 8% for the second, or Niger, falling from 89% for the first dose to 16% for the second. This problem does not only concern developing countries, however. The rate in Luxembourg falls from 99% to 86%, and in Belgium from 96% to 85%.

The fall in coverage from the first dose (usually given at birth or when a child is still very young) to following ones is one of the the biggest concerns for organisations such as the Strategic Advisory Group of Experts on Immunization (SAGE) at the WHO, who highlights this in their latest report, and to non-profit bodies working in this field such as Médecins Sans Frontières.

Parents and guardians should take children to be vaccinated at least five times in the first year of their life.

In its reports, the organisation includes the complex immunization schedule as one of the problems in accessing vaccines in countries with poor infrastructure and scant human and material resources. At present, parents and guardians should ensure to take children to be vaccinated at least five times in the first year of their life.

India, which accounted for 30% of deaths from measles in under four year olds in 2015, with a total of 22,703 fatalities, had an estimated coverage rate of 81% for the first dose and 69% for the second dose.

Pakistan, stronghold of polio

In neighbouring Pakistan, polio is reluctant to disappear entirely, although the first vaccine was invented in the 1950s. In 2016, just 42 cases of this disease were recorded worldwide. 21 of these cases were in Pakistan and another 13 just over the border with Afghanistan.

The remainder were recorded in Laos (3) and Nigeria (5). The latter cases, although isolated, are very important: just one year earlier, Africa celebrated the removal of Nigeria from the list of polio-endemic countries and the region took a first step towards eradicating the disease for good. Armed conflict in the country restrains medical services and organisations’ access to certain areas, making it nearly impossible to achieve the immunization rate and putting these populations in danger.

Although the end is near for this viral disease, it is imperative to maintain high immunization levels so that transmission becomes impossible and definitive eradication can be achieved. In April 2016, the vaccine was simultaneously switched globally by order of the WHO. Until that time it had protected against three serotypes of the disease, whereas henceforth it would only protect against two of those (types 1 and 3), as it was discovered some new cases of polio had their origin in the 2 serotype of the vaccine itself.

In 2015, the global immunization rate for the third and final dose of polio vaccination, which attacks the nervous system and causes paralysis which can affect the diaphragm and render breathing impossible, was 86% according to WHO estimates. Pakistan, one of the last strongholds of the disease, achieved 75% in 2015. The country has also seen some regressions as the 2013 levels of 66% were much lower than the 89% seen in 2011 and 2012. The countries with the worst coverage are Somalia (42%) and Equatorial Guinea (27%).

Somalia and Equatorial Guinea are also the countries with the worst vaccination rates (44% and 17% respectively), along with Ukraine, for the third dose of the DPT vaccine, which covers diphtheria, pertussis (whooping cough) and tetanus. Ukraine is another case of regression: the country saw its immunization rates drop sharply from 76% in 2012 to 23% in 2015.

The DPT vaccine requires three doses, with an additional booster dose also due in certain countries. As with measles, the vaccination rate falls sharply from the first dose to the final dose. In Guatemala, 96% of children received the first dose of the vaccination, a commendable figure and high enough to achieve herd immunity, but only 73% received the third dose of the vaccination. Panama is a similar case, the rate falling from 99% to 74%.

This vaccine protects from diphtheria, tetanus and whooping cough, three illnesses that remain present, although in some countries they sound like a bad memory from a bygone age. In 2015, over 10,000 cases of tetanus and over 4,500 cases of diphtheria were recorded worldwide. The figures for both diseases have fallen drastically, largely due to vaccines.

Whooping cough, on the other hand, continues to cause large numbers of illness and deaths in children, and figures have not improved in recent years. In some years, such as 2012 and 2014, the figures have actually increased. 142,412 cases were recorded in 2015. 56,696 children died, 15% of those from Nigeria.

The path to total eradication of a disease is long and paved with pitfalls. Because of this, it is important to remain vigilant, keep the shield strong and not become complacent about the fact that certain diseases have disappeared just because we no longer see them (or suffer them) in our immediate environment.

Since the measles vaccine was invented and introduced worldwide, the disease has nearly disappeared in certain regions and countries, to the point where many young people do not even remember it.

In other regions, where the situation had previously improved and the disease had been practically eradicated, outbreaks have rebounded. This was the case in Iraq in 1998 and 2009, linked to the problems of access and lack of resources before, during and after these conflict periods. Bulgaria had gone nearly a decade without a recorded case, when in 2009 the country saw a resurgence of measles with over 2,000 cases. In 2010, this figure reached 22,000, the greatest number ever recorded in the country.

In Mongolia, an outbreak in 2015 and extended to 2016 reported thousands of cases and killed more than a hundred people, most of them babies under eight months old, those who should have been protected by herd immunization. The lack of confidence in vaccines has much to do: 26.8% of those surveyed in that country for The Vaccine Confidence 2016 project were against the claim that the vaccines were safe.

Estimates sent by the country to the WHO claimed that the country’s coverage levels exceeded these minimum thresholds. But if the data is not accurate or population segments remain under the minimum threshold, the shield does not work either.

Whilst there are reasons to be optimistic in some areas, the difficulty of vaccinating all children in conflict zones or areas with a lack of resources or infrastructure, and to a much lesser extent, opposition to vaccines, does not allow for total eradication of diseases for which we have had a more than effective shield for decades. According to the WHO, 21.8 million babies do not receive the basic vaccinations.

The latest report from the WHO Strategic Advisory Group of Experts is categorical. It warns that the group remains “very concerned “ that “ progress toward the goals to eradicate polio, eliminate measles and rubella, and eliminate maternal and neonatal tetanus is too slow”. Global average immunization coverage has increased by only 1% since 2010.