Most flu vaccine in the United States is made from chicken eggs, using production methods that date back to 1945. This cumbersome technique requires 6-8 months of lead time to produce enough vaccine for the upcoming flu season. Every February, the World Health Organization and the Food and Drug Administration (FDA) make their best guess as to which flu strains should be covered by next winter’s vaccine, based on a review of circulating flu viruses from over 100 countries. But a lot can change in 8 months, especially with influenza. This past year, the “drifted” H3N2 influenza strain didn’t match up with the vaccine strain, explaining the vaccine’s poor performance.
Can researchers build a better flu vaccine? They probably already have. The FDA has approved two alternatives to traditional egg-based vaccines. One of these, Flucelvax, uses influenza virus grown in kidney cells that were originally obtained from a single cocker spaniel in 1958. The other one, FluBlok, is made by tricking insect cells into pumping out large amounts of hemagglutinin, which is then purified and used in the vaccine. These methods might sound outlandish, but they seem to be safe and effective.
These newer vaccines have several advantages:
They are safe for patients with egg allergies. Because most flu vaccine is made from eggs, many people with egg allergies can’t receive the traditional flu shot.
They don’t require a massive supply of chicken eggs, and could still be made even if a bird flu epidemic wiped out chicken flocks.
They need less manufacturing time than egg-based vaccines, meaning vaccine production could be ramped up quickly in case of a flu pandemic. This also might give the FDA more time to make their decision on which flu strains should go into the vaccine, reducing the risk of a vaccine–flu mismatch like last year’s.
Scientists are also working on a universal flu vaccine, one that might not need to be changed every year. This vaccine takes advantage of the fact that the H protein has two parts: a head region, which is the part that changes rapidly, and a stem region, which stays more or less the same. Small studies of vaccines using chunks of the stem have shown promising results in animals. Trials of these vaccines are just beginning in humans.