In a possible warning sign for the US and other countries in the northern hemisphere, the 2022 flu season in Chile started much earlier than usual and brought more hospitalizations than during the pandemic, but the effectiveness of the vaccine against hospitalization it was estimated at almost 50%, according to a new study published by the US Centers for Disease Control and Prevention.
Researchers look to the southern hemisphere when trying to forecast what flu season might be like in North America, and have noted that the southern season has been particularly bad this year.
n the study, published Thursday in the CDC Morbidity and Mortality Weekly Report, The researchers found that flu numbers in Chile were at epidemic levels in the first six weeks of the year, much earlier than in 2017, 2018 or 2019, when the flu season started in April or May. This year’s numbers fell in weeks seven to 17 before climbing back to epidemic levels in May and peaking in June.
Hospitalization rates for flu in Chile were “substantially higher” this year than in 2020 and 2021, the researchers say. Those pandemic years were marked by especially low numbers of viral illnesses worldwide due to Covid-19 mitigation measures, and experts warned that lifting those measures, and reducing exposure to viruses during the pandemic will cause infection numbers to rise again.
However, compared to the years before the 2017-19 pandemic, this year’s flu hospitalization rates in Chile were “substantially lower.” This is attributed in part to the vaccination of more than 92% of residents who were prioritized based on their age or underlying medical conditions, a group that made up 41% of the total population.
The influenza vaccine used in Chile, which included a match for the dominant A(H3N2) virus, was found to be 49% effective in preventing hospitalization. The shot used in the northern hemisphere includes the same clade of virus and antigen as the southern hemisphere vaccine, the researchers say, so it may be equally effective if the same virus dominates.
flu shot can prevent infection, and among those who still get the flu, vaccination can reduce the severity of illness and the risk of hospitalization.
The researchers say their findings should reinforce the need to prepare for an “off season” and urge health officials to encourage everyone to get vaccinated and avoid close contact with sick people.
According to data from the US Centers for Disease Control and Prevention, flu activity has already increased in the US about a month earlier than usual. Overall respiratory illness activity was “very high” in Washington, DC and “high” in seven states: Alabama, Georgia, Louisiana, New York, South Carolina, Tennessee and Texas.
More than 4% of lab tests came back positive for the flu in the second week of October, more than double in the past two weeks, but still not at last year’s peak positivity rate. Flu hospitalizations are also on the rise, but are not yet at last year’s peak.
So far, flu vaccination rates in the US are lower than they have been at this point in the season for the past several years: about 116 million doses of flu vaccine have been distributed, compared to 129 million at this point last year and 141 million in 2021.
Dr. Nipunie Rajapakse, a pediatric infectious disease specialist at the Mayo Clinic Children’s Center, told CNN Thursday that people should get vaccinated against Covid-19 and the flu and try to prevent any respiratory illness, especially as hospitalizations rise. due to RSV and other viruses. .
“Making sure your children and anyone older than six months in your family get a flu shot this year is even more important because we haven’t seen much flu in recent years, so everyone is going to start this season. with less immunity, less protection from previous infections,” Rajapakse said.