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Forskningsprojekt DAN-COMBO 2026 ENGLISH

Can a combination vaccine against both influenza and COVID-19 provide the same protection as two separate vaccines?

Danish version
In collaboration with the Research Unit at the Department of Cardiology, Herlev and Gentofte Hospital, and the University of Copenhagen, Danske Lægers Vaccinations Service (DLVS) is inviting Danish residents aged 65 years and older to participate in the DAN-COMBO study. The purpose of the study is to investigate whether a combination vaccine against influenza and COVID-19, given as a single injection, can provide protection against disease that is comparable to the current vaccines, which are administered as separate injections.
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People aged 65 years and older are recommended to receive annual vaccination against both influenza and COVID-19. Today, the vaccines are given as separate injections, but a combination vaccine may simplify vaccination and reduce the number of injections, which may be experienced as more convenient and less uncomfortable. However, knowledge is still lacking about how this approach works in practice and whether it provides the same or better protection against disease and complications such as hospitalization, pneumonia, and cardiovascular disease. DAN-COMBO aims to investigate this.

How the study works

The study will take place during the winter seasons 2026/2027 and 2027/2028 and will begin in October at all DLVS vaccination centers across Denmark. If you choose to participate, you will be randomly assigned to one of two groups. One group will receive a combination vaccine against influenza and COVID-19 as a single injection. The other group will receive a high-dose influenza vaccine together with a COVID-19 vaccine as two separate injections. You will be informed which group you have been assigned to on the day of vaccination.

You can register for the study online by booking an appointment. As part of the booking process, you may provide electronic consent to participate. It is also possible to provide consent in person at the vaccination site, after which the randomization will take place.

You can find answers to a number of general questions about the study in the Questions and Answers section at the bottom of the page. If you cannot find the information you are looking for, you are welcome to contact us by phone at 88 30 01 02. The phone line is open on weekdays from 9:00 AM to 3:00 PM.

Download participant information
Download participant information

Questions and answers:

When does the study with the combination vaccine begin?

You can register for the study of the combination vaccine against influenza and COVID-19 already today here on the website.

Once your registration has been completed, you can book an appointment at a vaccination site near you.

The vaccinations themselves will take place from mid-October, 2026, during the 2026/2027 season and from October 1, 2027, during the 2027/2028 season.

You can participate in the study regardless of where you live in Denmark. All vaccines will be administered at DLVS vaccination centres throughout the country. When booking your vaccination appointment, you may choose the vaccination centre closest to you.

You sign up by registering as a participant here on our website. Once your registration has been received, you can book appointments for the study visit at a location close to you. After booking, you will have the option to provide consent electronically from home.

The randomization between the two groups will take place only when you arrive for your vaccination visit. At that time, you will be randomly assigned to one of the two groups: either the combination vaccine (one injection) or a high-dose influenza vaccine together with a COVID-19 vaccine (two separate injections).

It is also possible to book an appointment, receive information, and provide consent in person at the vaccination site.

Yes. Participation in the study is entirely voluntary. You can cancel your appointment at any time if you no longer wish to take part.

By participating in the study, you will receive vaccination against both influenza and COVID-19 in accordance with current recommendations. As this is a randomized study, you will either receive a combination vaccine (one injection) or a high-dose influenza vaccine together with a COVID-19 vaccine (two separate injections).

The study therefore provides a unique opportunity to contribute to knowledge that may help evaluate future vaccination strategies against influenza and COVID-19.

Participants in the study are randomly assigned to one of two groups. One half will receive a combination vaccine against influenza and COVID-19 (one injection), while the other half will receive a high-dose influenza vaccine together with a COVID-19 vaccine as two separate injections.

The group assignment is determined randomly. You will be informed which vaccination you will receive during your vaccination visit.

After receiving your vaccination at one of our clinics — either the combination vaccine or a high-dose influenza vaccine together with a COVID-19 vaccine — you will be observed for a short period after vaccination in case you feel unwell as a side effect of the vaccination. If needed, our healthcare staff will be ready to assist you.

You will not need to attend any visits other than the vaccination appointment itself. All follow-up will take place through the nationwide Danish health registries, review of medical records, and completion of a short questionnaire. When the study has been completed, you will be able to find information about the results at the following link: https://minvaccination.dk/forskning/resultater

We expect to recruit approximately 410,000 participants during the winter seasons 2026/2027 and 2027/2028.

You can cancel your appointment at any time and without giving a reason. To do so, simply call us at 88 30 01 02.

Influenza and COVID-19 are infectious diseases that primarily affect the respiratory system and, in severe cases, may lead to hospitalization, particularly among older adults.

In collaboration with the Research Unit at the Department of Cardiology, Herlev and Gentofte Hospital, Danish Doctors Vaccination Service is conducting a clinical trial. The purpose of the study is to investigate whether a combination vaccine against influenza and COVID-19 can reduce the risk of illness and complications compared with the current vaccination strategy, in which the vaccines are given as separate injections (a high-dose influenza vaccine and a COVID-19 vaccine).

Among people aged 65 years and older, the study will investigate the risk of illness leading to contact with the healthcare system, as well as hospitalization due to influenza, COVID-19, respiratory disease, and cardiovascular disease, in addition to mortality.

No. You do not need to participate in this trial to receive the recommended influenza and COVID-19 vaccinations. You can also receive these vaccinations outside the trial through the national vaccination programme, for example at a regional vaccination site located at a hospital or by a private vaccination provider.

The study will take place at the clinics of Danske Lægers Vaccinations Service (DLVS) and is organized by the research unit at the Department of Cardiology, Herlev and Gentofte Hospital. The pharmaceutical company Moderna has donated the vaccines used in the study and funded other study-related expenses. It should be disclosed that the sponsor of the trial has previously received honoraria from Moderna for giving lectures.

Vaccination is associated with both benefits and possible side effects. Most side effects are mild and temporary, while more serious side effects are rare.

The most common side effects of the combination vaccine against influenza and COVID-19 are pain at the injection site, fatigue, muscle and joint pain, headache, chills, fever, as well as nausea and vomiting. Swollen or tender lymph nodes, typically in the armpit, may also occur. These side effects usually appear within the first few days after vaccination and typically last only a few days.

Vaccination is associated with both benefits and possible side effects. Most side effects are mild and temporary, while more serious side effects are rare.

The most common side effects of the COVID-19 vaccine are redness, swelling, and pain at the injection site, swelling and tenderness in the upper arm, joint and muscle pain or stiffness, nausea, vomiting, headache, fatigue, chills, and fever.

Vaccination is associated with both benefits and possible side effects. Most side effects are mild and temporary, while more serious side effects are rare.

The most common side effects of the high-dose influenza vaccine are pain, redness, and swelling at the injection site, as well as muscle pain, headache, and feeling unwell. Other common side effects may include fever, chills, and fatigue. These symptoms typically occur within the first few days after vaccination and usually disappear again within a few days.

The high-dose influenza vaccine contains four times as much inactivated influenza virus antigen as a standard-dose vaccine. This results in a stronger antibody response and therefore better protection against influenza.

If you feel unwell after receiving the vaccine, the healthcare professionals at our clinics are available to help you. If complications occur afterwards, the study doctor responsible for the trial will ensure appropriate follow-up.

We encourage all participants to read the leaflet “Your rights as a research participant in clinical trials involving medicines”, which has been prepared by the National Committee on Health Research Ethics, as well as the participant information document.

You do not receive payment for participating, and we do not offer any discount for taking part in the study. Participation in the study is completely free.

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Confirmation required

The target group for DAN-COMBO is individuals aged 65 years or older who have not yet been vaccinated against either influenza or COVID-19 in the current vaccination season.

To continue, please confirm the following:

  1. That you can understand spoken and written Danish or English.
  2. That you have not yet been vaccinated against influenza or COVID-19 in the current vaccination season.

I confirm all of the above

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