Most vaccination programmes continue to focus on reducing mortality and morbidity in children, even though the major burden of vaccine-preventable diseases is in adults. The changing demographics have raised concerns on the impact of aging populations on healthcare provision and healthcare budgets. Vaccination can help deliver significant decreases in healthcare utilisation, and improved quality of life.

However, there still remains a lack of awareness of the benefits of immunisation for adults. Adults need vaccination for various reasons:

1. Vaccination helps adults to stay healthy. Other than influenza, shingles (herpes zoster) and respiratory syncytial virus (RSV) infection cause significant morbidity and mortality by increasing the risk for other conditions, particularly cardiovascular and cerebrovascular diseases.
2. Immunity derived from vaccination during childhood wanes over time, and as we age the progressive decline of immune responsiveness also contributes to reduced immunogenicity and faster waning, resulting in increased risk for some infectious diseases.
3. Vaccination helps to protect family members and the community from infectious diseases. This is seen with increased pertussis in adults (due to waning immunity) correlating with increased risk of infection, illness and death from pertussis in infants. Thus, a lifetime risk may be addressed by life course vaccination.
4. Some adults can face greater risks to certain infections because of their work or underlying co-morbidities. Social factors such as exposure through travel for older persons or through clustering, from long-term care facilities or community living, may further exacerbate risks.

The primary objective for developing these clinical practice guidelines on adult immunisation is to assist doctors and the public in making decisions on the appropriate use of vaccines in the adult population from aged 18 years and above. These recommendations on adult immunisation are evidence-based, appropriate to the Malaysian context and reflect current best practices. As the global population, including Malaysia, is aging rapidly, this edition has also included a brief explanation on immunosenescence, that refers to the gradual decline in immune function with increasing age. It is hoped that the judicious use of vaccines will provide a cost-effective way of reducing the burden of morbidity and mortality due to vaccine-preventable infections among adults in Malaysia.

This is the fourth edition of the Guidelines For Adult Immunisation and we hope that it will continue to provide a useful resource for all doctors in Malaysia.

Yasmin A Malik
Editor-in-Chief
April 2026