Epidemiologists calculate how much data is needed to estimate the duration of vaccine protection

When designing a vaccination campaign, it is crucial to know how long the vaccine protection lasts. The research group of Matthieu Domenech de Cellès at the Max Planck Institute for Infection Biology in Berlin now showed how soon this duration of protection can be estimated from standard epidemiological data in the course of a vaccination campaign. In their studies, the researchers simulated the dynamics of the corona pandemic in Germany and found that differences in the individual duration of protection are an important factor to estimate the duration of protection. The results have now been published in the journal Royal Society Interface.

What are the important features of a vaccine? It should protect against infection and disease efficiently and do so as long as possible. When the first study results on vaccines against the coronavirus became available, hopes were high: some vaccines protected against infection and severe disease with an efficiency of up to 93%. What remained unclear, though, was how long this protection would last. The necessary data could only be collected over time, when the first vaccinated patients became infected again or when studies on the antibody concentration in their blood were available.

For this reason, Matthieu Domenech de Cellès wanted to find out what data would be sufficient to estimate this duration of protection. Together with his team at the Max Planck Institute for Infection Biology, the mathematician conducted a simulation study of the corona pandemic. The researchers adapted an existing mathematical model of corona transmission to simulate the incidence of infection in Germany after the start of the vaccination campaign. The model incorporated parameters such as transmission rates, infection duration and information from clinical trials of the vaccines. "We tried to bring in all the knowledge we had at that time," Domenech de Cellès said.

With their model, the researchers were able to track the development of the corona pandemic and verify at what point it was possible to correctly predict how long the vaccine protection would last. It was important to the researchers to estimate the duration of protection with regularly collected data. For their estimate, they simulated standard epidemiological data, such as those published by the Robert Koch Institute in Germany: corona cases per day and the age of the infected persons. Domenech de Cellès' team was thus able to show that the duration of vaccination protection can often be correctly estimated with less than one year of data after the start of the vaccination campaign.

With this information, vaccination campaigns may be managed more precisely in the future. Epidemiologists could be able to determine, for example, when to give booster vaccinations or when to rely on further initial vaccinations. Especially in times of vaccine shortage, this efficient planning is crucial.

In their study, the researchers also showed that differences in the individual duration of protection of the vaccinated were an important factor for their estimate. The immune system reacts differently to vaccinations on an individual basis―the degree of these differences is called immunological heterogeneity. Some people lose their vaccination protection after just a few weeks, while in others it lasts a lot longer. But until now, the main focus has been on the average duration of protection. Domenech de Cellès explains: "In future vaccination campaigns, it is crucial to also know the differences in duration of protection in order to assess the overall impact of vaccination."

Although the study focussed on assessing the impact of vaccines against emerging pathogens, the team's results can also help in understanding the dynamics of other vaccines. Domenech de Cellès’ research group is already working on designing models to study other vaccines, for example against measles, pneumococcus or pertussis.