World Immunisation Week, 24 to 30 April, provides an opportunity to highlight the critical role of vaccines. Vaccination programmes have been fundamental in protecting people against disease and preventing death. Now an essential part of healthcare globally, immunisation prevents 3.5 – 5 million deaths every year from diseases like diphtheria, tetanus, pertussis, influenza and measles.

For this year’s World Immunisation Week, the World Health Organization (WHO) is marking the  fiftieth anniversary of their Expanded Programme on Immunisation (EPI). This initiative aimed to ensure equitable access to life-saving vaccines for every child, regardless of where they live or whether or not they can afford healthcare. The programme has grown in this time from six childhood vaccines to now including vaccines for 13 diseases and 17 additional, context-dependant vaccines, which are vaccines that are recommended for particular settings, such as cholera.

Immunisation is one of the most cost-effective interventions available to save lives. Understanding the impact of vaccines can help to inform policymakers, programme delivery and improve cost-effectiveness.

Researchers from the Global Health Economics Centre and the Centre for Mathematical Modelling of Infectious Diseases at the London School of Hygiene & Tropical Medicine (LSHTM) are involved in an array of vaccine research. We spoke with some of our researchers about the importance of the EPI as well as some of their ongoing work. 

TB vaccines were one of the original vaccines included in the EPI. Dr Rebecca Clark, Research Fellow at LSHTM, said:

"The inclusion of BCG, a vaccine for tuberculosis disease,  in the EPI has been very important to help prevent morbidity and mortality from severe TB disease in young children and has contributed to high vaccine coverage rates throughout countries where it is still implemented. However, the highest burden of disease is in adolescents and adults. An effective vaccine that can prevent TB in those age groups is crucial to prevent spread of the disease and accelerate the declines in global TB rates.

“In my work in the TB Modelling Group, we generate evidence on the potential impact of introducing novel TB vaccines to support decision-makers and promote investment. We estimated the health impact, cost and cost-effectiveness, impact on health equity, and macro-economic impact of introducing a new TB vaccine in 105 low- and middle-income countries and found that overall, new TB vaccines could have a positive impact on reducing deaths from TB, could be cost-effective, reduce health inequities, and promote economic growth.  These results have been used to support global investment in upcoming Phase 2b and Phase 3 trials to ideally have a new vaccine licenced for use by the end of the decade."

Over the past 50 years, the EPI has expanded to now include vaccines for 13 diseases. One of these is vaccines for COVID-19 in adults, Dr Yang Liu, Assistant Professor at LSHTM, said:

“I am an infectious disease modeller working on evaluating the impact of COVID-19 vaccines in over 100 low- and middle- income countries. We hope to find the best ways to implement vaccination and to strengthen policies in the coming years in the context of potential emerging variants of concern so that we can minimise the disease burden. During the COVID-19 pandemic, countries introduced a variety of COVID-19 vaccines in their first round of vaccination campaigns and many experienced severe roll-out delays. In this context, the strategy moving forward is of great interest to country’s government and international organisations.

“There is a lot of uncertainty about the immune response to SARS-CoV-2. Over the past year or two, the decrease in surveillance efforts globally has only made studying it even more difficult. Closely monitoring emerging variants, population-level disease burden, and measuring the effectiveness of the vaccine in preventing infection or severe disease will all be important evidence for us to evaluate the COVID-19 vaccine’s impact and cost-effectiveness. The routine vaccination programme will be critical to ensure the cost-effectiveness and delivery of this vaccine product now that we are out of an emergency response setting.”