Anvisa (National Health Surveillance Agency) defined which strains (types of virus) should be included in vaccines against influenza, the flu virus, that will be used in Brazil in 2026.
Changing the composition of strains is fundamental to the effectiveness of the vaccine, as the virus adapts and mutates. The WHO (World Health Organization) regularly analyzes all subtypes of the flu virus that circulate most frequently, to improve the effectiveness of immunization.
Every year, Anvisa, in accordance with the WHO, publishes the composition of the influenza vaccines that will be used in the following year. The composition for 2026 was published in Normative Instruction 408/2025.
Vaccines for the Southern Hemisphere (2026 season)
Vaccines destined for the southern hemisphere and used in Brazil from February 1, 2026 must contain:
• Trivalent vaccines: strains similar to A/Missouri/11/2025 (H1N1)pdm09, A/Singapore/GP20238/2024 (H3N2) and B/Austria/1359417/2021 (Victoria lineage).
• Quadrivalent vaccines: in addition to these three, the addition of a strain similar to B/Phuket/3073/2013 (Yamagata lineage).
• Non-egg-based vaccines: strains equivalent to A/Missouri/11/2025 (H1N1)pdm09, A/Sydney/1359/2024 (H3N2) and B/Austria/1359417/2021 (Victoria lineage).
The labels of immunizers must indicate: “CEPAS 2026 SOUTHERN HEMISPHERE”.
Vaccines for the Northern Hemisphere (2025–2026 season)
Vaccines with strains recommended for the northern hemisphere are intended exclusively for Ministry of Health campaigns for specific regions of the country. They must contain:
• Trivalent vaccines: strains similar to A/Victoria/4897/2022 (H1N1)pdm09, A/Croatia/10136RV/2023 (H3N2) and B/Austria/1359417/2021 (Victoria lineage).
• Quadrivalent vaccines: addition of a strain similar to B/Phuket/3073/2013 (Yamagata lineage).
• Non-egg-based vaccines: strains equivalent to A/Wisconsin/67/2022 (H1N1)pdm09, A/District of Columbia/27/2023 (H3N2) and B/Phuket/3073/2013 (Yamagata lineage).
In these cases, the labels must contain the expression: “CEPAS 2025-2026 NORTHERN HEMISFÉRIO”.
Tetravalent vaccines
Anvisa warns that the WHO recommendation also foresees the discontinuation of the use of tetravalent versions of the seasonal influenza vaccine from 2027. According to the agency, the decision is related to the absence of confirmed records of the natural circulation of the B/Yamagata strain — exclusive to quadrivalent immunizers — since 2020.
The organization, however, emphasizes that a transition period may be necessary until the definitive withdrawal of these immunizers, depending on the regulatory assessment and operational capacity of each country.
In the case of Brazil, after analyzing the current availability of trivalent and tetravalent seasonal influenza vaccines registered on the market, Anvisa considered it necessary to maintain the supply of tetravalent versions throughout 2026. Immediate withdrawal could compromise vaccination coverage nationwide, both in the public and private networks, as the markets are not equally supplied with both versions.
