Critical evidence to strengthen seasonal vaccination in Americas

Burden of disease estimates and vaccine effectiveness studies can generate significant evidence on the need and proven benefit of immunization, which can be used to inform decision-makers and strengthen seasonal vaccination programmes. Throughout the COVID-19 pandemic, PAHO has supported countries in WHO’s Americas Region to do both.

Demonstrating need

PAHO provided guidance on how to monitor both influenza and SARS-CoV-2 using existing acute respiratory infection surveillance systems. This is particularly valuable for monitoring epidemiological trends including disease severity and for assessing the impact of the pandemic on health systems.

An additional layer of work focused on supporting countries to estimate the burden of COVID-19 and influenza and on understanding how these data can most effectively be presented to national authorities for use in prevention and control decision-making.

In 2020–2021, several countries completed studies on the medical burden of influenza, which have the potential to improve the reliability of national burden estimates, identify at-risk populations, and inform national policies to reduce the socioeconomic impact of the disease. In Chile, the Ministry of Health also did a study on the economic burden of influenza, which was used to develop national public health priorities and actions.

Proving benefit

In addition to generating evidence to demonstrate the need for seasonal vaccination programmes through burden of disease studies, countries in the Americas are working to generate evidence to prove the benefit of these programmes through vaccine effectiveness studies. Since 2012, as part of the regional REVELAC-i and SARInet networks, countries in the region have made significant progress in measuring influenza vaccine effectiveness through a multi-center evaluation based on existing SARI sentinel surveillance platforms. Now regional estimates of influenza vaccine effectiveness have been adapted to include COVID-19.

Vaccine impact estimates, determined by the number of hospitalizations avoided by the immunization campaign, complement the information on vaccine effectiveness to give health authorities comprehensive and critical data that can justify investments in influenza vaccines and guide decision-making for influenza and COVID-19 prevention programmes the region.

For both burden of disease and vaccine effectiveness, individual country experiences will continue to provide a vital source of learning that can help inform and guide other nations aiming to use evidence in support of seasonal influenza vaccination.

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