Combining Influenza and COVID-19 vaccination (ComFluCOV) study

Please note that recruitment to this study is now complete.

What is the purpose of this research study?

There are now vaccines that have been approved to protect against COVID-19 in the UK. The duration of protection of these COVID-19 vaccines is unknown but further booster doses may be required to give continued protection.

With the challenges of immunising large numbers of people against COVID-19 and the need to continue the seasonal influenza (flu) vaccination schedule, it would be preferable if we could give people both their COVID-19 booster and flu vaccine at the same appointment.

This would mean receiving two vaccines on the same day, one in each arm.  It would also mean fewer appointments for those who need both vaccines and would reduce the burden on the NHS.

Therefore, the purpose of the ComFluCOV study is to see what side effects, such as fever and tiredness, people get when they are given their second dose of the COVID-19 vaccine at the same time as the currently recommended flu vaccine. We will also look at people’s immune responses to both vaccines given together.

We will be enrolling people aged 18 years and over. We particularly welcome participants from all communities and those with underlying health conditions who would usually be offered the influenza vaccine. To take part, you must have already received your first dose of either the Pfizer/BioNTech COVID-19 vaccine or the Oxford/AstraZeneca COVID-19 vaccine and be awaiting your second dose.

Am I suitable to take part?

Adults that are aged 18 and over and have had their first dose of either COVID-19 vaccine currently in use in the UK mass vaccination programme may be able to take part.

In order to be enrolled in the study, you must:

  • Have received one dose of either:
    • Oxford/AstraZeneca (ChadOx1) within 56 to 90 days prior to study enrolment
    • Pfizer/BioNTech (BNT162n2) within 28 to 90 days prior to study enrolment
  • Be willing to tell local research staff about your medical history. You may be asked to allow the local research staff to check this with your General Practitioner (GP)
  • Be able to regularly access and use an electronic device (e.g. smart phone, laptop, tablet) to complete study procedures
  • Agree not to donate blood for 1 week following visits 1 and 2.

For further details about the study and if you can take part please see the Participant Information Leaflet on the individual study site pages.

Summary of the study

We hope to recruit 756 participants into the study from at least 5 UK NHS sites.

  • Participants will attend 3 study visits around 3 weeks apart at their nearest participating hospital.
  • Participants will be randomly allocated to one of two groups:
  • One group will receive a flu vaccine with their second COVID-19 dose at Visit 1, and then a saline injection (placebo) at Visit 2.

Note: The saline injection (placebo) is a salt and water solution which looks like the flu vaccine but does not contain any active ingredients.

  • The other group will receive a saline injection (placebo) with their second COVID-19 dose at Visit 1, and then a flu vaccine at Visit 2.
  • A participant’s group will be chosen at random by a computer. This is so that we can be sure that participants in the two groups are as similar as possible and can be compared fairly.
  • The second dose of COVID-19 vaccine given in the study will be the same as the one the participant received as their first dose in the UK mass vaccination programme
  • Participants will not know in which order they receive the flu vaccine and the placebo injection.
  • A blood and saliva sample will be taken at each study visit to look at the immune responses to the vaccines.
  • Participants who could become pregnant will also be required to take a urine pregnancy test at visit 1 and inform the study team if they become pregnant during the study.
  • Participants will need to complete a daily online diary for seven days after each vaccination visit.
  • The study will take roughly 6 weeks to complete for each participant (from the time the first dose of vaccine is given to the third visit).
  • We will not be offering diagnostic COVID-19 testing as part of this study, but it is important that participants in this study access COVID-19 testing outside of the study following normal government guidance if necessary.
  • We cannot guarantee that the flu vaccine received through this study will protect you against flu through the 2021/22 flu season. We advise that you accept your next NHS flu vaccine as usual, where relevant.

What vaccines are being used in this study?

The vaccines used in this study are:

Influenza (flu) vaccines from the UK 2020/2021 flu season

Flucelvax QIV (recommended for people aged under 65 years old) 

This vaccine contains four of the main strains of the flu virus that has caused infection over the winter. The vaccine contains parts of the influenza viruses that our immune system can ‘see’ and make protective responses against which can provide protection in the future.

The viruses that are used to make the vaccine are inactivated which means that they cannot cause infection. This type of vaccine is usually offered to healthcare workers and those with underlying medical problems who are at increased risk of flu.

Flublok QIVr (recommended for people aged under 65 years old)

This vaccine contains four of the main strains of the flu virus that has caused infection over the winter. The vaccine contains parts of the influenza viruses that our immune system can ‘see’ and make protective responses against, which can provide protection in the future. The parts of the virus used are manufactured using the genetic material of the virus and cannot cause infection. This type of vaccine is usually offered to healthcare workers and those with underlying medical problems who are at increased risk of flu.

FluAd (MF59) (recommended for people aged over 65 years old) 

This vaccine contains three of the main strains of the flu virus that has caused infection over the winter. In addition to the inactivated parts of the flu virus this vaccine also contains an additional substance (an adjuvant) which is added to the vaccine to enhance the body’s immune response. This is particularly important as we get older as our immune responses to both natural infection and vaccines weaken.

Influenza vaccines are usually given once a year to provide protection against infection during the flu season, which is typically over the winter months, but there is no reason why the vaccine cannot be given more than once a year.  The protection provided by the flu vaccine is typically less than 6 months so even if you have already had the flu vaccine this year you can safely have another dose as part of this study.


Saline injection (Sodium Chloride 0.9%)

A saline injection will be used as a placebo, this contains a salt-water solution. This is a harmless solution routinely used in healthcare.

COVID-19 approved vaccines

ChAdOx1 nCoV-19 (Oxford/AstraZeneca)

The AstraZeneca vaccine is made from a weakened version of a common cold virus from chimpanzees that has been genetically changed so that it is impossible for it to grow in humans.

Added to this virus are genes that make proteins from the COVID-19 virus called Spike proteins, which play an essential role in infection.

Through vaccination, the body recognises and develops an immune response to the Spike protein that will help stop the COVID-19 virus from entering human cells and therefore prevent infection.

This is the vaccine that is commonly known as the “Oxford vaccine”.  It has been tested in more than 20,000 people worldwide as part of the COVID-19 vaccine trials. It has been found to be both safe and efficacious in preventing COVID-19.

BNT162b2 (Pfizer/BioNTech)

This is a new kind of vaccine which uses a small amount of the genetic coding material (mRNA) of the COVID-19 virus spike protein packaged inside very small fatty particles called lipid nanoparticles. When these are injected into your body, your cells take up these fatty particles, and start producing the Spike protein.

The immune system “sees” these spike proteins, and makes a protective immune reaction against them.

The original mRNA that has been taken into your cells is broken down within a few days, and cannot be incorporated into your own genetic code.

This vaccine has been tested in more than 40,000 people worldwide and has been shown to be both safe and efficacious.

Neither vaccine contains the SARS-CoV-2 coronavirus and therefore cannot give you COVID-19

What are the side effects of the COVID-19 and Flu vaccines?

Common side effects

Following vaccination, people very often have tenderness, pain, warmth, redness, itching, swelling or bruising or less commonly have a small lump in their arm where they have been vaccinated.

Other common side effects

Some people can develop these symptoms after vaccination. They usually last for less than a week, and more commonly 24-48hours.

  • Fatigue
  • Headaches
  • Flu-like symptoms, such as high temperature, sore throat, runny nose, cough and chills
  • Muscle aches
  • Joint aches
  • Feeling unwell (malaise)
  • Feeling sick or nauseated, vomiting or diarrhoea

Other less common side effects include:

  • Abdominal pain
  • Decreased appetite
  • Feeling dizzy
  • Swollen lymph nodes (glands) e.g. in the neck or armpit
  • Excessive sweating, itching skin or rash

These symptoms can be reduced by use of paracetamol around the time of immunisation and over the next 24 hours.

After immunisation with the Pfizer/BioNTech vaccine, difficulty sleeping has been observed in fewer than 1 in 100 people, and weakness of the muscles on one side of the face has been observed in fewer than 1 in 1000 people.

What are the advantages of taking part?

The information gained from the study will make a valuable contribution to the pandemic response and help us to determine whether it is safe and effective to give the influenza (flu) vaccine at the same time as the COVID-19 vaccine.

The protection given by the influenza vaccine is unlikely to last until the flu season so if applicable to you, we advise that you still accept your next influenza vaccine appointment when you are invited.

Are there any risks from taking part in the study?

In addition to the potential side effects of the vaccines outlined above, the blood samples taken in the study may cause slight pain and occasionally bruising.  Please refer to the participant information leaflet for full details of procedures and potential risks.

What will happen if I don’t want to carry on with the study?

If, at any time after agreeing to participate, you decide that you do not want to carry on with the study, you are free to stop taking part, without giving a reason.

Withdrawing from the study will not affect your routine medical care or rights. Unless you state otherwise, any blood and saliva samples taken whilst you have been in the study will continue to be stored and used for research as detailed above. You are free to request that your study samples are destroyed at any time during the study.

Your data would be managed as laid out in the participant information leaflet section ‘What will happen to my data’.

What’s next?

If you are interested in taking part in this study, please click on the following link to find a study site.

This study is funded by the National Institute for Health Research (NIHR). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.