“The previous year’s vaccine will not necessarily provide protection against the strains circulating this year. That’s why it’s important to get the flu vaccine with each new campaign. The 2024 flu vaccine formulation is made up of the strains that are predominant in the southern hemisphere: two strains of influenza A and one strain of influenza B, which tends to cause an exacerbation of the flu in young children.”says Butantan’s medical security manager, Karina Miyaji.
The flu is an acute infection of the respiratory system caused by the influenza virus, which has a high potential for transmission. Influenza can be types A, B, C or D and correspond to more than 30,000 different subtypes.
Viruses are made up of proteins called hemagglutinin (HA) and neuraminidase (NA) and can cause the same symptoms as the disease. Types A and B are those that affect humans and at least 3 cause disease: H2N2, H1N1 and H3N2.
H1N1 pandemic
Vaccination is capable of controlling the spread of Influenza, such as that which occurred in relation to influenza A (H1N1) between 2009 and 2010. WHO declared the disease a pandemic in June 2009, after the virus caused outbreaks in North America and quickly spread around the world.
“The new strains of influenza that cause pandemics originate from genetic reassortments of viruses from animals such as pigs and wild birds”explains Karina.
At the time, contrary to typical seasonal flu patterns, Influenza A (H1N1) caused high levels of infections in the northern hemisphere summer and even higher levels of activity in the colder months. The new virus also caused more severe symptoms and higher mortality not seen in recent influenza infections.
In Brazil, H1N1 was detected in May 2009, initially concentrated in the South and Southeast, but then spread throughout the country. Throughout that year, almost 60,000 cases and more than 2,000 deaths were recorded. Pregnant women, the elderly and people with chronic diseases were the main victims.
“The gestational state causes several immunological, endocrinological and hormonal changes that make the pregnant woman more susceptible to infections and more intense symptoms in the case of influenza infection. Vaccination prevents these complications in the pregnant woman and offers a double advantage to the baby.”said Karina Miyaji.
Vaccination contained pandemic
The pandemic was contained with the production and supply of vaccines, which began to be developed in the second half of 2009 and offered to several countries in 2010, including Brazil.
At the time, the federal government signed a licensing and technology transfer agreement for the Influenza vaccine from the pharmaceutical company Sanofi Pasteur to the Butantan Institute and, in 2010, the PNI (National Immunization Program) acquired 83 million doses of the H1N1 vaccine.
The WHO declared the end of the influenza A (H1N1) pandemic in August 2010, thanks to the success of vaccination. Around 18,000 deaths from the disease were officially reported from April 2009 to August 2010 worldwide.
“Vaccination campaigns begin with priority groups because they can develop very serious cases of influenza. We saw this in the last H1N1 influenza pandemic in mid-2009 and 2010, when many people became ill due to the disease and we saw several deaths among pregnant women.”says Karina Miyaji.
Currently, Butantan manufactures more than 80 million doses of the Influenza vaccine every year, which are distributed via the PNI (National Health System) by the SUS (Unified Health System). As the influenza A (H1N1) virus continues to circulate among humans on the planet, it continues to be included in the vaccine formulation and recommended annually, especially for the most vulnerable groups.
Elderly and children: biggest victims of H1N1
THE InfoGripe Bulletinfrom Fiocruz (Oswaldo Cruz Foundation), shows that Influenza A (H1N1) is responsible for the majority of deaths from SARS in children under 2 years old and elderly people over 65 years old this year.
“In the population aged 5 to 64, the presence of the influenza A virus predominates among deaths from SARS”states the bulletin for epidemiological week 32 (4 Aug 2024 to 10 Aug 2024).
Influenza is linked to a high rate of hospitalization in children because they do not yet have immunity to fight the virus.
“Young children may respond poorly to the flu due to the immaturity of their immune systems, just as pregnant women, whose immune systems are already altered by hormones and changes during pregnancy, can respond poorly to the flu. In healthy people, in addition to providing protection, vaccination helps them to survive the disease without symptoms or to alleviate symptoms.”said Karina Miyaji.
In the elderly, the flu tends to be more serious basically because of a phenomenon called immunosenescence, which is the decline in immune defenses that occurs with advancing age and comorbidities, which makes them more likely to become seriously ill in the event of the flu.
“Most hospitalizations due to influenza are among elderly people. This occurs mainly due to the weakening of the immune system that occurs with aging, associated with comorbidities such as diabetes, lung problems, kidney and liver problems, which help to further weaken the immune system.”concludes Karina Miyaji.
With information from Butantan.
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