Covid-19: is the reactive vaccination strategy the solution?

in collaboration with

Dr Gérald Kierzek (Medical Director of Doctissimo)

For the past few weeks, and after a short lull, the Covid-19 epidemic has been in full swing. The number of cases is on the rise daily and the lifting of health restrictions is still in order. However, the effective R, which measures the circulation of the virus, has gone back above 1, which means that the viral circulation is important. And the strategy of mass vaccination of the population has reached its limits.

Even if it is not perfect, the vaccine against Covid-19 protects against serious forms of the disease. A team of French researchers conducted a study on how to conduct a new vaccine strategy to convince the unvaccinated to take their vaccine doses. It is reactive vaccination, which consists of offering the vaccine to people close to an infected case. The results of their work are published in the journal Nature Communications on March 17.

A valid model when vaccination is weak

To carry out their study, the researchers started from INSEE data (sociodemographic characteristics, professional situations, social contacts, but also vaccination coverage, characteristics of the disease, etc.) and built a mathematical model. Depending on the dynamics of the epidemic, which created different scenarios, to assess the impact of a reactive vaccination strategy.

In all scenarios, the reactive vaccination strategy works best, especially when vaccination coverage is low. Indeed, when it is strong, most relatives of the infected person will already be vaccinated.

A vaccine incentive

For the researchers, even if the strategy is not perfect, it can encourage unvaccinated relatives to the vaccine. “The model that we have built makes it possible to consider reactive vaccination as an effective strategy to increase vaccination coverage and to reduce the number of cases in certain epidemic scenarios, especially when it is coupled with other measures such as effective tracing of contact cases” explains Chiara Poletto, Inserm researcher and last author of the study. “This is a tool that could also be reused and adapted in France in the event that another variant emerges and where the effectiveness of a reactive strategy should be tested to administer possible booster doses. This modeling may also be of interest to other countries with socio-demographic characteristics similar to France, in which vaccination coverage is lower.

“It should not be a public health strategy” for Dr Kierzek

For Dr Gérald Kierzek, emergency doctor and medical director of Doctissimo on the contrary, it is not useful to vaccinate people not at risk. “Innate immunity, which varies from one individual to another, is very difficult to integrate and anticipate using a mathematical model, so we cannot draw conclusions from this type of purely theoretical and statistical study. We have clearly seen the limits of these approaches in the management of the pandemic. This kind of study is only one parameter of the decision and should above all no longer guide public health policy! We must move away from “all vaccination” to move towards personalized vaccination strategies for people at risk; redo medicine, therefore. We will have other waves of virus, inevitable and without gravity if the most fragile are protected and treated quickly. It is useless or even harmful to scare yourself with this kind of results” concludes the doctor.