January 29, 2021 1:08:57 pm
Vaccinations against 10 major pathogens have a substantial impact on public health in low-income and middle-income countries (LMICs), according to new modelling research published in The Lancet.
The study estimated that from 2000 to 2019, vaccinations have prevented 37 million deaths, and that this figure will increase to 69 million deaths for the period of 2000-2030. Most of this impact is estimated to be among children younger than five years, most notably from measles vaccinations.
Vaccines are cost-effective health interventions that substantially reduce death and illness from a range of diseases. The new study involved 16 independent research groups modelling the impact of childhood vaccination programmes in 98 LMICs. The study assessed the impact of vaccination programmes against 10 pathogens: hepatitis B (HepB), haemophilus influenzae type B (Hib), human papillomavirus (HPV), Japanese encephalitis (JE), measles, neisseria meningitidis serogroup A (MenA), streptococcus pneumoniae, rotavirus, rubella virus and yellow fever virus (YF).
According to the study, as a result of the vaccination programmes, those born in 2019 will experience 72 percent lower mortality from the 10 diseases over their lifetime if there was no immunisation. By taking this 2019 birth cohort and using the UN World Population Prospects demographic estimates, the study said mortality in children under five in the 98 countries would be 45% higher in the absence of vaccination against the 10 pathogens.
Dr Caroline Trotter from the University of Cambridge, UK, and a co-author of the study said: “There has been a much-needed investment in childhood vaccination programmes in low-income and middle-income countries (LMICs) and this has led to an increase in the number of children vaccinated. Our modelling has provided robust evidence on the effectiveness of vaccination programmes in LMICs and indicated what might be lost if current vaccination programmes are not sustained.”
Multiple models were applied for each pathogen (20 models in all). The estimates of impact were based on the past and future coverage of individual vaccines, vaccine effectiveness and data on deaths caused by the diseases, and on the years of healthy life lost due to premature death and disability from the diseases (DALYs). By comparing a scenario with no vaccination programmes in place to scenarios when vaccinations programmes had been implemented, the study estimated the impact on deaths and on DALYs.
The study used two methods to assess the impact to provide both a cross-sectional (yearly) and longer-term (lifetime) view of the impact. The first method assessed the difference in the number of deaths between the vaccination and no vaccination scenarios for each year and then totalled these annual results.
The second method assessed the long-term impact of vaccination by summarising impact over the lifetime for groups of people who were born in the same year between 2000 and 2030 and then calculated the difference between vaccination and no vaccination scenarios.
Results demonstrated that between 2000 and 2019, there was an increase in the average number of vaccines received per child, both for existing vaccines such as measles, and for new vaccines such as rotavirus. Considering the impact per year, the study estimates that from 2000 to 2030, vaccination will have prevented 69 million deaths from the 10 diseases, 37 million of which were averted between 2000 and 2019. Vaccinations against measles had the biggest impact, preventing 56 million deaths between 2000 and 2030.
In terms of the impact of vaccination over the lifetime of people born between 2000 and 2030, the study estimated that vaccination will prevent 120 million deaths, of which 65 million are in children younger than five years. 58 million of deaths would be prevented by measles vaccines and 38 million by hepatitis B vaccines.
The study also examined the relative impact of each vaccine and demonstrated that measles, Hib and pneumococcal conjugate vaccines (PCVs) have the largest impact on deaths of children under five. Vaccines against HPV, hepatitis B and yellow fever have the largest impact per person vaccinated over lifetime.
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