While in baseball it’s three strikes and you’re out, it’s not quite the same with flu vaccines. Though one of the targeted flu strains is slightly mismatched, this season’s flu shot offers a great deal of protection. A Loyola Medicine flu expert says the current flu vaccine is still in the game and will keep people well and on the playing field.

The trivalent vaccine is the most commonly used vaccine and targets three flu virus strains: two flu A strains – H3N2 and H1N1 – and one flu B strain. There is also a quadrivalent flu shot that targets the three strains in the trivalent but also protects against a second flu B strain.

“The current flu shot is not a loser and should not be benched as ineffective,” said Jorge Parada, MD, MPH, FACP, FIDSA, FSHEA, hospital epidemiologist and medical director of the Infection Control program at Loyola University Health System. “While there was a mismatch due to a mutation in the H3N2 strain, there are actually two H3N2 strains in circulation, complicating the interpretation of the accuracy of the vaccine.”

The Centers for Disease Control (CDC) reports that flu activity is “high” or “widespread” in 43 states and call it an epidemic this season. Most of the reported flu cases are caused by the H3N2 strain.

“Nearly one-third of circulating H3N2 viruses matches the strain found in the current vaccine, meaning the vaccine is doing its job,” Parada said. “One hundred percent of the H1N1 circulating strain matches that in the current vaccine, earning a home run for those keeping score.” However, to date, only a small portion of the flu cases reported to date have been identified as H1N1.

“To those who think there is no point because it is a mismatch, I answer that it is only a partial mismatch and it still offers protection for the multiple flu strains circulating out there,” said Dr. Parada.