Potential New Tool To Fight Covid And Flu

As a healthcare provider I had my first covid shots pretty early. I had been warned to expect a pretty vigorous immune response and it didn’t disappoint—within about 18 hours I was shivering and my muscles ached. This lasted for about a day, and then I was back to normal. This has been my response every time I’ve gotten the shot. When I finally did catch covid I felt that way for about 2 weeks, in addition to having a horrid cough. But I didn’t end up in the hospital. The vaccine was well worth it.

Covid vaccines have been shown over and over to be safe and effective—effective at preventing severe disease and death, but not necessarily at preventing getting sick at all. That’s a good goal, and a win all around. But current vaccine uptake isn’t great for a number of reasons.

We do need new tools. The unpleasant reaction I get to the covid shot is common and a barrier for many. We do have an alternative—the Novavax protein-based vaccine. Well, maybe we do and maybe we don’t. Robert Kennedy’s HHS has thrown unnecessary roadblocks in the way of this safe and effective alternative. 

But unpleasant reactions and dangerous leaders aren’t the only barriers to vaccination. We need to make shots easy—they have to be available, cheap/free, and not laden with side-effects. Lots of my patients prefer not to get more than one shot at a time. This is fine but it does increase the risk that they will miss shots. Enter a combined covid+flu shot.

When we use combination shots people are much more likely to get recommended vaccines. Most of us would rather have a single needle stick. Last season a combo flu and covid shot was tested, but the flu component failed to measure up to the usual solo flu shot. So how did this new vaccine do?

The new shot is an mRNA vaccine, like the current Pfizer and Moderna covid shots. There are lots of advantages to using mRNA vaccines. Current flu shots are not mRNA based, but are grown in chicken eggs. This is a time consuming, fairly inflexible process. An influenza mRNA vaccine would allow us to much more flexibility—currently we need to decide on what strains we use many months in advance and hope that next season’s flu viruses don’t surprise us with a lot of changes. If they do, an mRNA platform allows us to make rapid changes, something not possible with traditional flu vaccines.

So, in theory, having a combined shot allows us flexibility to deal with changing viruses, and improves vaccine uptake in the population—it’s just easier to get a single shot. What this study did not do is measure clinical vaccine efficacy. I wrote earlier about the need to ask the right questions when you design a study. This new study was a “Phase 3” trial, where a smaller number of people were given either the new shot or the separate flu and covid shots. The were evaluated for side effects and other safety measures, and their blood was tested for markers of immunity. Blood tests are not the same as looking at real life outcomes such as decreased risk of death and hospitalization, but they are a useful surrogate.

The researchers found that the new combo shot was very effective at causing the desired immune reaction in people. Side effects were basically mild, but where both more frequent and stronger than in the separate shots. The level of antibodies against the flu viruses was actually higher than in the traditional flu shot. There may be a tradeoff here—more convenience and better (presumed) efficacy, but more notable side effects.

The next step is going to be determined by regulators. It’s not clear whether they will allow the vaccine to be marketed for the 2026-27 flu season based on these data, or if, as Kennedy has hinted, they will be required to do a large scale, expensive trial first. This would give us more data on real world efficacy against the viruses and would give us a better idea on the significance of the annoying-but-not-dangerous side effects. But it would also delay the release quite a bit, and increase the cost.

The one thing I fear is that Kennedy will require a “placebo-controlled trial”. This would mean that volunteers would get either the new shot or a dummy shot. This poses significant ethical problems. We have here two dangerous diseases that both have a well-tested, effective vaccine available. In a placebo-controlled trial, participants who receive the placebo would be denied both the new shot and the older effective shots. We don’t like to do this and the ethical implications aren’t great.

My sense is that baring interference from the antivaccine activists in charge of HHS, this combination shot will be in use in the next year or two and will be a great alternative that will improve vaccine uptake, and help reduce the burden of these dangerous infectious diseases.

Stay well.

-pal

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Rudman Spergel AK, Wu I, Deng W, et al. Immunogenicity and Safety of Influenza and COVID-19 Multicomponent Vaccine in Adults ≥50 Years: A Randomized Clinical Trial. JAMA. Published online May 07, 2025. doi:10.1001/jama.2025.5646