The priority objective of the vaccines against COVID-19 is to prevent serious illness, hospital admissions, hospitalizations in intensive care and associated mortality. For this purpose, those with the highest mortality, that is, over 70 years of age, with 86% of the mortality, should be vaccinated. Mortality due to COVID-19 is fundamentally associated with ageing, which, as a biological consequence of immunosenescence, accumulates, as age advances, comorbidities (due to the persistence of a chronic pro-inflammatory state), increasing the risk of serious disease and death.

The priority vaccination of this population has a direct effect in reducing the risk of death and an indirect effect in decreasing transmission to close cohabitants (recent studies have shown a reduction in the number of infected and viral load in those infected by people close to those vaccinated, in comparison with the period prior to vaccination).

For any vaccine, the priority factor is the reduction of cases of serious illness and death. In the context of COVID-19, vaccination by age groups, in decreasing order, satisfies the main objective of a vaccination plan. In relation to COVID-19, no more seriousness has been demonstrated for chronic diseases, in particular higher mortality, with the exception of hypertension, cardiovascular diseases, and chronic respiratory diseases that permanently require oxygen support, end-stage renal failure, obesity and decompensated diabetes compared to the general population.

For example, the rates of serious illness, hospitalization and mortality in HIV persons infected with COVID-19 are identical to those with profound immunodeficiency and to those with a relatively well-maintained immune status. We conclude that other factors, such as old age, comorbidities and social factors are the drivers of risk, more than the degree of immunodeficiency itself. In the meantime, the pandemic is not fed by the elderly, given that the prevalence of infection is around 80% in the youngest. While the vaccine is not available for this population more susceptible to infection, generally with asymptomatic or paucysymptomatic evolution, non-pharmacological preventive measures – distancing, wearing masks, testing, screening and isolation - have to accompany this vaccination phase. This will ensure that the return to “normal life” is faster, before group immunity is reached (at the expense of infections and the escalation in vaccination of the youngest), while ensuring the protection of the most vulnerable.

Francisco Antunes

Retired Professor of Infectious Diseases