If you were a virus, would you live in emptied Spain or in overcrowded New York City? It is clear that in the city of lights viruses will find more hosts to spread. As we can see, the place where we live and the time determine our life.
In addition to our family, we live with economic, environmental and sociodemographic factors typical of our environment. These factors are responsible for inequalities in the population that, in turn, influence the spread of diseases and the prevention measures available to us.
Importance of spatio-temporal studies
COVID-19, like so many other diseases, is affecting some areas of the world more than others. We know this thanks to studies that analyze them by geographical areas over time. Much of this variability between regions is influenced by the environment and characteristics of each population.
In this sense, space-time studies offer us very specific information, something similar to taking a patient’s temperature. With the advantage that, depending on the results, important decisions can be made and preventive measures, such as vaccination, can be promoted or evaluated.
Without these spatio-temporal analyzes, how are we going to answer the question of whether it is effective to get a flu vaccine in July? How would we know if there are enough vaccinated in our area of residence to affirm that we are (or not) protected against a certain disease?
Let’s talk about rotavirus
Rotavirus is the most common cause of hospitalization for severe cases of diarrhea in children around the world. Currently, it is responsible for thousands of deaths each year in developing countries. Since 2007 we have had two safe and effective vaccines that have substantially reduced hospitalizations for rotavirus. However, only in 98 countries are they included in universal vaccination programs. Spain is not one of them.
The decision to vaccinate a child against rotavirus is influenced by several factors. The recommendation of our pediatrician and / or our financial possibilities will be decisive in our decision. But the environment, for example our country of residence, will also play a very important role. It is also very likely that if our neighbor vaccinates his children, we will do it too. This happens because we share a residence area and we are more alike than we think. It will not be strange that we even share the same pediatrician and have a similar economic situation.
The Vaccine Research Area of the FISABIO Foundation has carried out in the Valencian Community the first spatio-temporal study that analyzes the impact of the rotavirus vaccine in hospitalizations due to acute gastroenteritis and rotavirus. For this, we have studied what has happened to rotavirus since the appearance of the vaccine in each area of residence, delimited by the area of the health center.
Now, when analyzing the data, how do we know that it is vaccination that is reducing hospitalizations for rotavirus and not other factors? As we have stated, vaccination is not solely responsible for more or less admissions due to rotavirus or acute gastroenteritis in some areas or in others. The environment influences.
Specifically, there is a variability that is given by differences between hospital admission policies, proximity to the hospital and other socio-demographic, economic or environmental factors. Including them in “the image” has allowed us to make a correct evaluation of the vaccination. In addition to avoiding biases in the vaccine impact estimates.
The impact
For the Vaccine Research Area study, data from 721,471 children under 3 years of age were analyzed, of which 189,247 were vaccinated against rotavirus. The main conclusion was that the introduction of rotavirus vaccines prevented approximately 1,866 hospitalizations potentially attributable to this virus. The data can be viewed interactively on the dynamic maps of the RotApp application.
The analysis also revealed significant reductions in hospitalizations for rotavirus and acute gastroenteritis of 36% and 20% respectively during 2015-2016, when vaccine coverage was around 50%. These reductions would have been 86% and 47%, respectively, if the entire population had been vaccinated.
As we said, the place and time in which we live condition our lives (and our infections). Not including this information in impact studies would jeopardize the evaluation of prevention measures such as vaccination , whether we have decided to live in emptied Spain or in overcrowded New York City.
Mónica López Lacort, Statistician in the Vaccine Research Area, Fisabio
This article was originally published on The Conversation. Read the original.
