In 2017, the number of children immunized – 116.2 million – was the highest ever reported. The Region of the Americas achieved maternal and neonatal tetanus elimination, leaving only 15 countries yet to achieve elimination. Since 2010, 113 countries have introduced new vaccines, and more than 20 million additional children have been vaccinated.
Nevertheless, this year starkly illustrates how easily hard-won gains are lost. Because of low coverage nationally, or pockets of low coverage, multiple WHO regions have been hit with large measles and diphtheria outbreaks causing many deaths. The continued detection of circulating vaccine-derived poliovirus is further evidence that national immunization programmes are not achieving the goal of reaching every child.
The Global Vaccine Action Plan set ambitious goals, and it remains the case that most targets will not be met by the end of the Decade of Vaccines in 2020. DTP3 and first-dose measles vaccine coverage have plateaued globally at 85%. Progress towards the eradication of wild poliovirus and the elimination of measles, rubella, and maternal and neonatal tetanus is currently too slow to be achieved by the end of the decade.
The 2018 Assessment report of the Global Vaccine Action Plan provides an update on work to achieve universal vaccination. Strategic Advisory Group of Experts on Immunization. Geneva: World Health Organization; 2018 (WHO/IVB/18.11). Licence: CC BY-NC-SA 3.0 IGO
Global Vaccine Action Plan
One of the five goals of the Global Vaccine Action Plan is to develop and introduce new and improved vaccines and technologies. The R&D focus is on potentially vaccine-preventable diseases responsible for a high global burden of disease, including malaria, HIV/AIDS, TB and seven other priority infections, and new technologies to facilitate vaccine delivery or wider use of vaccination.
The most advanced malaria vaccine, RTS,S/AS01 (Mosquirix®), has achieved a positive scientific opinion from the European Medicines Agency and is undergoing pilot implementation studies in three African countries. There are some concerns about its efficacy and safety, and further studies may be required to evaluate alternative dosing regimens and schedules. Multiple other vaccine candidates are at various stages of clinical evaluation, targeting different points in the malaria parasite life cycle.
Vaccine development for HIV remains an immense technological challenge, not least because of its great variability and mutability. However, the field has taken heart from the RV144 trial in HIV, the first to demonstrate protective efficacy, albeit modest. The laboratory identification of broadly neutralizing antibodies – recognizing multiples strains of HIV – has provided further impetus. As well as enabling studies that are informative for vaccine design, broadly neutralizing antibodies could be manufactured and used directly in prevention. The HIV vaccine pipeline includes multiple candidate vaccines undergoing clinical and pre-clinical evaluation.
Although a vaccine for TB, BCG, already exists, the current forms offer incomplete protection and have several drawbacks. Different vaccines may also be required to achieve different objectives in TB, such as prevention of initial infection or prevention of activation of latent TB. A wide range of candidate vaccines are progressing through clinical evaluation, with several showing positive results in early phase clinical trials.
Progress towards a universal flu vaccine has been more challenging, although a variety of vaccine candidates are in early stages of clinical evaluation.
Benefit of Eliminating Polio
Successful and sustained eradication of polio carries significant humanitarian and economic benefits: with no child ever again suffering polio paralysis, and upwards of US$ 50 billion saved, those funds can be used to address other public health needs.
Failure to sustain eradication would have significant consequences, however, with global resurgence of the disease, and as many as 200 000 new cases every single year, all over the world, within a period of ten years. That is why full implementation of resolution WHA71.16 on containment of polioviruses is so important.
One in five children in the world are still not fully protected by even the most basic vaccines. About 22 million are at risk of contracting preventable diseases because they are under-vaccinated. This allows 1.5 million children to die every year from diseases that can be prevented by vaccination coverage.
Many rural areas in the world that do not have reliable power supplies. Vaccines need to be kept at particular temperatures, usually refrigerated, to remain effective. Cold chain conditions aren’t possible without power. A cold chain is a temperature-controlled supply chain that runs from the time the vaccine is produced until it’s administered. It holds the vaccines in a temperature of between 2°C and 8°C.