Three types of influenza viruses – A, B, and C – cause infections in humans. Although influenza A virus is the main type associated with infections during seasonal periods, as of 2020, influenza B virus was considered the causative agent of about a quarter of annual influenza cases.
During the onset of the COVID-19 pandemic, cocirculation of the two distinct lineages of influenza B viruses, B/Victoria/2/1987 (B/Victoria) and B/Yamagata/16/1988 (B/Yamagata), decreased significantly. According to data from the FluNet tool, which is coordinated by the World Health Organization, since March 2020 the isolation or sequencing of viruses belonging to the Yamagata lineage was not conclusively carried out.
Specialists like John Paget, PhD, from the Netherlands Institute for Health Services Research (Nivel) in Utrecht, have indicated that determining the extinction of the B/Yamagata lineage is critical. There is the possibility of a reintroduction of the lineage, as has occurred in the past with the reemergence of influenza A (H1N1) in 1997, which could represent a risk in subsequent years.
“In the next few years, research related to viruses such as influenza B and the impact on population immunity will be important. Let’s remember that influenza changes every year due to its characteristics, so a lack of exposure will also have an impact on the development of the disease,” said Martínez Jiménez.
Vaccination is essential
According to Dr. Comas, the only way to overcome the immunity gap phenomenon is through vaccination campaigns. “There is no other way to overcome the phenomenon, and how fast it is done will depend on the effort,” he said.
“In the case of COVID-19, it is not planned to vaccinate children under 5 years of age, and if we do not vaccinate children under 5 years of age, that gap will exist. In addition, this winter season will be important to know whether we are already endemic or not. It will be the key point, and it will determine if we will have a peak or not in the summer.
“In the case of the rest of the diseases, we need to correct what has been deficient in different governments, and we are going to have the resurgence of other infectious diseases that had already been forgotten. We have the example of poliomyelitis, the increase in meningeal tuberculosis, and we will have an increase in whooping cough and pertussislike syndrome. In this sense, we are going back to the point where Mexico and the world were around the ‘60s and ‘70s, and we have to be very alert to detect, isolate, and revaccinate.”
Finally, Dr. Comas called for continuing precautionary measures before the arrival of the sixth wave. “At a national level, the sixth wave of COVID-19 has already begun, and an increase in cases is expected in January. Regarding vaccines, if you are over 18 years of age and have not had any vaccine dose, you can get Abdala, however, there are no studies on this vaccine as a booster, and it is not authorized by the Mexican government for this purpose. Therefore, it is necessary to continue with measures such as the use of face masks in crowded places or with poor ventilation, and in the event of having symptoms, avoid going out and encourage ventilation at work and schools. If we do this, at least in the case of diseases that are transmitted by the respiratory route, the impact will be minimal.”
Martínez Jiménez and Dr. Comas have disclosed no relevant financial relationships.
This article was translated from the Medscape Spanish Edition.
A version of this article first appeared on Medscape.com.