CDC Study Suggests Vaccination Offers More Protection Against Covid Than Prior Infection
Research indicates that flu vaccination at two years of age may offer added protection against infection with a form of flu virus not previously known to be resistant to vaccine.
Image credit: CDC.
When flu infects the respiratory tract, sometimes patients will experience high fever, difficulty breathing, lethargy, and difficulty sleeping. In the United States, most influenza activity usually occurs at the beginning of the fall, when children begin kindergarten.
A small segment of people may get flu with a different strain, called a “resistance strain.” Some flu viruses are highly mutable and are capable of developing resistance to vaccines. For years scientists have sought ways to thwart the effects of potential resistant flu viruses.
A new study funded by the Centers for Disease Control and Prevention (CDC) indicates that flu vaccination offered protection against resistance to a flu virus that researchers thought was resistant to conventional vaccines. The findings appear in the journal Molecular Psychiatry.
The researchers used samples from 52 healthy people, ages 18 to 49, who had either received an influenza vaccine in recent years or never received one. For three weeks after the immunity, they had influenza-like illness and tested for resistance to the virus.
Results showed that immunity to the resistance strain had disappeared in the group vaccinated, likely meaning that the vaccine is now having an effect against the resistant strain, said lead author Michael Y. Liu, Ph.D., associate professor of epidemiology at the Rollins School of Public Health, Emory University.
“The long-standing challenge in fighting flu is that resistance occurs and new strains are constantly emerging,” Liu said. “We’ve made great progress against other strains, but this strain, with the newly emerging activity in 2019, continues to present a major risk to the immune system of any susceptible person. Vaccination still remains the best tool for protection against the flu.”
“One of the risks of vaccination is that the virus, if introduced, could become resistant in your body. Our study suggests that flu vaccination, in a subset of patients, provides the potential to counteract and ‘step in’ to boost other protective factors in the immune system,” said Thomas R. Frieden, M.D., M.P.H., CDC director. “This study provides further proof that the best way to protect yourself from flu is to get vaccinated each year.”
This study involved 124 virus-negative healthy adults in the United States from 2015 to 2016. The participants, who received either a seasonal influenza vaccination or placebo injection at the time of vaccination, were examined at baseline, during a 21-day period after vaccination, and then one year later. During that year, they all had lower total flu hospitalizations.
The study had one limitation: In this cohort, the researchers did not have a control group. That group is small, but as Dr. Liu noted, in the larger group of patients in the U.S., many people may not receive flu vaccine. In that case, the results for the observed subset may not be translated to the general population.
Purchasers of the FDA-approved flu vaccines must vaccinate against all strains of the influenza virus for protection against common strains each year. To protect against a new flu strain, seasonal influenza vaccines are designed to protect against four flu viruses in four categories. Two candidates, H3N2, one of the most common strains in the current influenza season, and H1N1, one of the most common strains in the 2015-2016 season, are included in the lowest two categories. For protection against a third viral, pandemic, influenza strain, two candidates, the antigenicity (how well the vaccine stimulates an immune response) and immune status (how well the immune system recognizes the influenza virus in the circulating population) of the immune system are taken into account. The high-risk groups (such as patients with existing severe or chronic health conditions or pregnant women) also receive higher-level protection against the virus.
The study was funded by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.