Influenza has returned to Europe at a faster-than-expected rate this winter after almost disappearing last year, raising concerns about a prolonged “twindemic” with COVID-19 amid some doubts about the effectiveness of flu vaccines, Report informs.

The return of the virus could be the start of an unusually long flu season that could stretch well into the summer, the ECDC’s top expert on influenza Pasi Penttinen told Reuters.

“If we start to lift all measures, the big concern I have for influenza is that, because we have had such a long time of almost no circulation in the European population, maybe we will shift away from normal seasonal patterns,” he said.

He said dismantling restrictive measures in the spring could prolong the circulation of flu far beyond the normal end of the European season in May.