NEW DELHI: The flu virus that infected millions, particularly children, has mysteriously vanished from the face of the Earth. Experts are so convinced that it is gone that they believe it should be removed from vaccines altogether. This virus, known as the Yamagata lineage, was one of four flu viruses commonly included in annual influenza vaccinations. However, it went completely silent in March 2020, coinciding with the global lockdown due to the Covid-19 pandemic.
The precautions taken to prevent the spread of Covid-19, such as wearing masks and practicing social distancing, resulted in historically low flu cases. In fact, one of the flu viruses, the Yamagata lineage, was eradicated completely. The Yamagata lineage belongs to the influenza B family tree, which also includes the Victoria lineage. Although these viruses are not the most deadly or rapidly evolving, they tend to cause more illness in children who have not been exposed to them as much as adults.
In contrast, the influenza A viruses, such as H1N1, are more concerning and have the potential to cause pandemics. For instance, the 1918 ‘great flu’ pandemic claimed the lives of approximately 50 million people. The Yamagata lineage, being a ‘B’ virus, has never caused a pandemic. Therefore, the US Food and Drug Administration (FDA) and the World Health Organisation (WHO) have agreed that it is no longer necessary to include it in seasonal flu vaccines.
The FDA has strongly recommended influenza vaccine manufacturers to remove the B/Yamagata lineage virus from the upcoming 2024-2025 influenza season. This move from quadrivalent to trivalent vaccines will reduce the number of flu strains covered by the vaccines from four to three. It is hoped that this change will enable manufacturers to increase their production capacity and provide more doses.
Dr Hana El Sahly, the chair of the FDA advisory committee, emphasized the importance of not vaccinating individuals against a virus that has not been in circulation for several years. However, some members of the pharmaceutical industry have argued that manufacturers will need time to transition to the new vaccine formula. The Government’s Green Book also stated that trivalent vaccines are clinically suitable.
In conclusion, the disappearance of the Yamagata lineage flu virus has led to a recommendation to remove it from seasonal flu vaccines. This decision is based on the fact that the virus has not caused a pandemic, unlike the influenza A viruses. Although some challenges may arise during the transition to trivalent vaccines, it is expected that this change will increase vaccine production. The ultimate goal is to ensure that vaccines are effective against the viruses that are currently in circulation and pose the greatest threat to public health.