In a possible sign for the US, flu hospitalizations in Chile were the highest in three years, but the vaccine was 49% effective against hospitalizations.


In a warning sign for the US and other countries in the Northern Hemisphere, Chile’s 2022 flu season started much earlier than usual and led to more hospitalizations than in the pandemic, but vaccine effectiveness against hospitalizations was estimated to be nearly 50%, according to the CDC. A new study published by the US Centers for Disease Control and Prevention.

Researchers look to the Southern Hemisphere in an attempt to predict what North America’s flu season might look like, noting that this year’s season in the south has been particularly bad.

In the study, published Thursday in the CDC’s Morbidity and Mortality Weekly Report, 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 flu season began. in April or May. This year’s numbers fell in weeks seven to 17, before rising again to epidemic levels in May and peaking in June.

Flu hospitalization rates in Chile were “significantly higher” this year than in 2020 and 2021, researchers say. Those pandemic years saw particularly low numbers of viral diseases worldwide due to measures to mitigate Covid-19, and experts warn that lifting those measures – and reducing exposure to viruses during the pandemic – will restore infection rates.

However, compared to the pre-pandemic years of 2017-19, this year’s flu hospitalization rates were “significantly lower” in Chile. This is partly due to the vaccination of more than 92% of residents who were prioritized due to age or medical conditions, a group that made up 41% of the total population.

The flu vaccine used in Chile, including one that matches the main A(H3N2) virus, was 49% effective in preventing hospitalization. The shot used in the Northern Hemisphere contains the same virus clade and antigen as the Southern Hemisphere vaccine, researchers say, so it may be effective if the same virus is prevalent.

The flu vaccine can prevent infection, and among those who still get sick with the flu, the vaccine reduces the severity of the illness and the risk of hospitalization.

The researchers say their findings should reinforce the need to prepare for an “atypical 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 picked up in the US about a month earlier than usual. Overall respiratory disease activity was “very high” in Washington, and “high” in seven states: Alabama, Georgia, Louisiana, New York, South Carolina, Tennessee and Texas.

More than 4 percent of lab tests came back positive for the flu in the second week of October, more than double the previous two weeks, but still not the highest positivity rate of last year. Hospitalizations for the flu are also on the rise, but still not at last year’s peak.

So far, the flu vaccination rate in the US is lower than it has been this season in recent years – about 116 million doses of the flu vaccine have been distributed, compared to 129 million and 141 million at this time last year. 2021

Dr. Nipunie Rajapakse, a pediatric infectious disease specialist at the Mayo Clinic Children’s Center, told CNN on Thursday that people should get vaccinated against Covid-19 and the flu and try to prevent any respiratory illness, especially as hospitalizations from RSV and other viruses are on the rise. while they are doing it. .

“Making sure your children and anyone in your family over the age of six months is getting the flu shot this year is even more important because we haven’t seen a lot of flu in the last couple of years, so everyone is going into this season with less immunity, less protection from previous infections.” , said Rajapakse.