News – Peer Review / Symbolism or Modeling / People
- A new modeling study has estimated that between 2000 and 2030 vaccines against 10 major pathogens – including measles, rotavirus, HPV and hepatitis B – will have prevented 69 million deaths in countries with low-income and middle-income (LMICs).
- The study estimated that, as a result of vaccination programs, those born in 2019 will experience 72% lower mortality from the 10 diseases over their lifetime than without a vaccine.
- Vaccination was estimated to have the greatest impact in children under five – mortality from the 10 diseases in this age group would be 45% higher than currently seen without vaccines, according to the research .
- This is the largest-scale modeling study of vaccine effects in LMIC to date, evaluating vaccination programs against 10 pathogens within 98 countries. The findings show that, if the progress in vaccine coverage is sustained, these public health benefits will continue to increase in the coming decades.
Vaccines against 10 major pathogens have significant effects on public health in low- and middle-income countries (LMICs), according to a new modeling study published in The Lancet. The study estimated that between 2000 and 2019 vaccinations have prevented 37 million deaths, and that figure will rise to 69 million deaths for the period 2000-2030. Most of these effects are thought to be present in children younger than five years, especially from the measles vaccine.
Vaccines are cost-effective health interventions that significantly reduce death and illness from a range of diseases. International programming has broadcast standard childhood vaccines in LMIC and impact descriptions are needed to inform future investment. Measuring direct impact is difficult due to limitations in disease data and surveillance systems. Mathematical models can provide valuable estimates of impact based on data on disease burden and vaccine coverage.
The new study involved 16 independent research groups shaping the impact of childhood immunization programs in 98 LMICs. The study evaluated the impact of vaccination programs against ten 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 (YF) virus.
Dr Caroline Trotter from Cambridge University UK, co-author of the study, said: “There has been significant investment in childhood immunization programs in low- and middle-income countries (LMICs). and this has led to an increase in the number of children receiving the vaccine. To inform future investment and ensure its continuity we need to assess the impact of these programs on public health. Our modeling has provided strong evidence on the effectiveness of vaccine programs in LMIC and has shown what could be lost if the routine vaccination programs are not maintained. ” [1]
Multiple models were applied for each pathogen (20 models in total) [2). Estimates of impact were based on 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) [3]. By comparing the situation without vaccine programs in place when vaccine programs were implemented, the study estimated the impact on mortality and DALYs.
The study used two methods to assess impact to provide a cross-sectional (year) and long-term (longevity) view of impact. The first method assessed the difference in the number of deaths between vaccinated and non-vaccinated conditions for each year and then these annual results were aggregated.
The second method assessed the long-term effects of vaccines by summarizing the over-life effects of groups of people born in the same year between 2000 and 2030 and then measuring the difference between vaccines and non-conditions. vaccine. This approach allowed for a vaccine effect to be introduced later in life, which is particularly relevant for diseases such as hepatitis B or HPV where there is a long delay between infection and adverse outcomes. Most of the effects of the hepatitis B vaccine will be seen after 2030 and the effects of HPV will be seen after 2040.
Results showed that, between 2000 and 2019, there was an increase in the average number of vaccines received per child, both for conventional vaccines such as measles, and for newer vaccines such as rotavirus.
Considering the impact each year, the study estimates that, from 2000 to 2030, vaccines will have prevented 69 million deaths from the 10 diseases, 37 million of which were canceled between 2000 and 2019. Anti-measles vaccines had the greatest impact, preventing 56 million deaths between 2000 and 2030.
In terms of the impact of vaccines over the lives of people born between 2000 and 2030, the study estimated that the vaccine will prevent 120 million deaths, 65 million of which are in children younger than five years. 58 million deaths would have been prevented by measles vaccines and 38 million by hepatitis B vaccines.
Considering those born in 2019, the study estimated that an increase in vaccine coverage and the introduction of additional vaccines resulted in a 72% reduction in lifetime mortality caused by the 10 pathogens. By giving birth to this 2019 group and using UN World Poppect Prospects demographic estimates [4], the study estimated that mortality in children under five in the 98 countries would be 45% higher without vaccination against the 10 pathogens.
The study also examined the relative effects of each vaccine and showed that measles, Hib and pneumococcal conjugate vaccines (PCVs) have the greatest impact on deaths in children under five. Vaccines against HPV, hepatitis B and yellow fever have the greatest impact for everyone who has been vaccinated over a lifetime.
Corresponding author, Professor Neil Ferguson of Imperial College London, UK, said: “Our study highlights the significant public health benefits of vaccination programs in countries with Low-income and middle-income By starting up to 2030 in these 98 countries we will have provided an insight into where investments in vaccine coverage should be directed to reap additional benefits, for example by increasing HPV coverage in girls and pneumococcal conjugate (PCV) vaccines in children under five have the greatest effect according to our model. ” [1]
Co-author Dr Katy Gaythorpe, also from Imperial College London, UK, said: “By estimating the higher mortality rate if vaccine programs were not in place, our study has shown the importance of Maintaining high coverage will require continued political commitment, funding, public participation to promote the benefits and safety of vaccines, and programs to deliver vaccine education, training and guidance. ” [1]
Researchers described the degree of uncertainty from data on disease burden and from structural assumptions of the different models but were unable to assess uncertainty in demographic estimates and estimates of vaccine coverage in the future. past and future. The study identified a number of limitations, for example for those countries where specific vaccines have not been introduced, the study assumed that they would reach the same coverage as a reference vaccine, which could mean too much. overlap. Moreover, no models reported a difference in vaccine coverage by geographic area or aggregation of hard-to-reach groups. Researchers highlighted the need for future models to confirm effects for different population populations within countries in order to achieve more accurate estimates.
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