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Taking people in SwedenPhase 4

How well the flu vaccine works in adults with obesity

Tests the immune response to Influvac flu vaccine in adults with obesity.

Key facts

Who runs it
Region Stockholm – SLSO
Where
Stockholm, SwedenSee the site
Registry title
Evaluation of Influenza Vaccine Immune Response in Obesity (VaccObFlu)
Status
Recruiting
Phase
Phase 4
People taking part
120 people, planned
Started
5 Oct 2026
Expected to end
30 Jun 2027
Type of study
Interventional
Record updated
8 July 2026

Who can take part

AI summary

From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.

The trial is looking for adults aged 18-50 years in several groups: people with obesity, people with type 2 diabetes, non-obese people, and pregnant women after week 12. They will get the Influvac flu vaccine, and the immune response is measured.

Age
18-50 years at inclusion (the registry lists 18 to 64 years).
Sex
All sexes can join. Women who can have children must use adequate contraception (Groups 1, 2 and 3).
Disease stage
Obesity means a BMI of 30 kg/m2 or more (Groups 1, 4 and 6). Type 2 diabetes is needed for Groups 2 and 6. Non-obese means a BMI of 18.5-29.9 kg/m2 (Groups 2, 3 and 5). Pregnant women must be past week 12 (Groups 4 and 5).
Earlier treatment
Group 6 must use a GLP-1 analogue. People cannot join if they had the flu vaccine this season (September-April), a blood transfusion in the last 6 months, or immunoglobulin in the last 6 months. Another vaccine less than 14 days before (inactivated) or 30 days before (live) also rules people out. Antibiotics in the last 12 weeks also rule people out.

Main reasons for not taking part

  • Allergy to Influvac, or confirmed anaphylaxis after egg or a flu vaccine
  • Confirmed flu infection this season (September-April)
  • Illness or medicine that weakens the immune system
  • Cancer now or in the past 5 years (some exceptions)
  • Pregnancy before week 12

The registry criteria, word for word

Show all 24 criteriaShow less

Who can take part

  • The subject is able to give their written consent to participate in the trial
  • For female subjects of fertile age, adequate contraception should be used (Groups 1, 2 and 3)
  • Obesity as defined by BMI ≥30kg/m2 (Group 1 and Group 4 and Group 6)
  • Aged 18-50 years at inclusion
  • A diagnosis of diabetes mellitus type 2 (Groups 2 and Group 6)
  • For groups 2, 3 and group 5 non-obese as defined by BMI 18.5-29.9kg/m2
  • Pregnant after week 12 (Groups 4 and 5)
  • Use of GLP-1 analogue (Group 6 only)

Who cannot take part

  • Documented receipt of influenza vaccine in the current season September-April
  • Receipt of another vaccine less than 14 days prior to study vaccination in the case of inactivated vaccines or 30 days in the case of live vaccines
  • Antibiotic use in the previous 12 weeks
  • Pregnancy prior to week 12
  • Confirmed anaphylaxis after exposure to egg or after previous influenza vaccination
  • Disease, condition or concomitant medication known to cause immunosuppression
  • Any other pre-existing disease or medical condition judged by the trial investigator as being a contra-indication for study participation
  • Confirmed influenza infection during the current season September-April
  • Unable to give informed consent due to either language barrier or condition affecting the ability of the potential participant to understand, retain or communicate their consent as judged by the study investigator
  • Allergy to Influvac
  • Current or previous malignancy within the past 5 years (with the exception of CIN I or II cervical pre-cancerous lesions, or skin cancers in situ)
  • Receipt of blood transfusion within the preceding 6 months
  • Participation in another clinical trial during the study period
  • Planned move during the study period that would prohibit participating in the study for its full duration
  • Participation of any study personnel or their immediate dependents, family or household members as well as any family relations to the sponsor or the PI
  • Receipt of Immunoglobulin within the preceding 6 months

Check if you might fit

Answer for yourself. This is not a decision: only the study team can say whether you can take part.

  • Are you between 18 and 64 years old?

Where in Sweden

  • Region Stockholm – SLSOStockholm, SwedenTaking people

About the trial

What the trial wants to find out

To describe changes in Hemagglutination Inhibition Assay (HAI) geometric mean titre (GMT) after Influvac, including the proportions of participants achieving a protective titre ≥40 and the proportion of participants achieving a 4-fold rise in titre at 14 days post vaccine.

Questions to ask the study team

  1. How often do I need to come in, and for how long each time?
  2. Are travel costs paid?
  3. Can I keep my own doctor?
  4. What happens if I want to stop?

Contact the study team: see the registry record

Print a page for my doctor

Data and sources

Registry record
Listed on the EU's official list of trials (CTIS).
Official title
Phase IV open-label clinical trial of the immunogenicity and safety of standard dose trivalent inactivated influenza vaccine (Influvac) in a population of people with obesity
Plain-language title
How well the flu vaccine works in adults with obesityGenerated from the registry record. The registry title is the official one.
AI summary
From the trial's eligibility criteria. Read by machine on 9 November 2026.
Fit questions
Built from 2025-522698-13-00, who can take part
Record updated
8 July 2026