Flu and COVID booster jabs work together

A booster programme for the COVID-19 vaccine has been implemented in the UK. But, doctors are predicting a worse-than-usual flu season this year, so we’re being urged to grab a jab for flu too. And the current guidance is that this can safely be given alongside a COVID booster. Chris Smith heard from Rajeka Lazarus at Bristol University who has been a part of the ComFluCOV study, which has been testing this and has just announced their results...

Rajeka - By giving the vaccines together, you can prevent any delays while getting protection for one infection or the other, and also, hopefully, make it easier for people to get both vaccines just by having one appointment. Also, it makes it easier, hopefully, for the healthcare services, by reducing the number of appointments they need to deliver.

Chris - Indeed, because the JCVI, our Joint Committee on Vaccination and Immunisation, have said that this should be done where it is clinically expedient to do so, but obviously people shouldn't wait to get both vaccines. If they can have one sooner, they should just go and get that one a bit sooner, shouldn't they? But how did you actually do your study? Because critically one wants to know, if we are going to give two vaccines at the same time, that both are going to work equivalently well.

Rajeka - That's right, and I think it's important to say that giving two vaccines at the same time is very common. People will get a pneumonia vaccine or a shingles vaccine alongside their flu vaccine. But when there's a new combination, it does need to be tested. So we invited volunteers who were due to have their second dose of the COVID-19 vaccine, and then randomised them to have that second dose alongside a flu vaccine or a placebo, which was just a salt solution. And then compared the responses of those volunteers to how they react to the vaccine, and also their immune response in blood tests that we took.

Chris - Let's start with the first of the points you make about the reaction. This is side-effect profile, I presume: sore arm, feeling a bit achy and tired. What happened there? Did people get a double whammy with the side effects if they had both at the same time or were they okay?

Rajeka - We know that with the COVID-19 vaccines, depending on which one you had and whether it's a first, second dose, that you can get kind of a more general flu-like symptoms with them. And those are the symptoms that we were most interested in, as well as to see whether having the flu would increase the number of people who got those symptoms. And it varied a little bit, but overall, we found that there wasn't a significant increase when you have them both together compared to having the COVID-19 vaccine alone. Where there was an increase, most of those side effects were still mild or moderate.

Chris - And perhaps most critically, when you followed up and tested people's blood for evidence of immunity against both flu and coronavirus, was there any difference in giving the vaccines individually or when they were administered together?

Rajeka - That's a really important question. Overall, there wasn't a difference when you gave the vaccines together compared to when you gave the COVID-19 vaccine alone, which means that the protection that you get from both those vaccines remains intact.

Chris - How long after the vaccines were administered did you look though, because one of the other key questions here is how long are people going to be protected for?

Rajeka - Yeah, that's right. So we checked three weeks after people had had the vaccination, because we're just looking at how people respond in terms of their antibody levels in the blood. And I suppose what's really important in terms of how long it lasts is really how long people stop getting disease for; how well the vaccine works. And that's not something that we tested in our study. At this time, we don't know what level of antibody or immune response you need to provide protection from COVID. So that's the kind of question that we need to answer by ongoing studies, looking at what happens in the real world.