Seasonal vaccinations: flu and COVID boosters explained

Why these vaccines are seasonal

Flu and COVID are different from vaccines like tetanus that last for years, and there are two main reasons. First, the viruses change: flu in particular mutates constantly, and new variants of the COVID virus keep emerging, so the vaccines are reviewed and updated to match the strains expected to circulate. Second, the protection from these vaccines fades over months, so a top-up is needed to keep immunity strong when the risk is highest. Flu and COVID both spread most in autumn and winter, when people mix indoors, so the NHS times its programme to build protection before that peak. This is why being vaccinated last year does not mean you are protected this year — a fresh dose keeps your defences up to date.

Who is offered them

The NHS focuses seasonal vaccines on the people most likely to become seriously ill, and the exact eligible groups are set each year. They typically include older adults, people with certain long-term health conditions such as heart, lung, kidney or liver disease, diabetes, or a weakened immune system, pregnant women, and carers. Young children are offered a flu vaccine, often as a nasal spray, both to protect them and to reduce spread. Frontline health and social care workers are usually offered vaccination too, to protect them and the vulnerable people they care for. Eligibility can change from year to year, so it is worth checking the current NHS advice or asking your GP or pharmacist whether you qualify this season.

How the vaccines protect you

Vaccines work by teaching your immune system to recognise part of a virus, so that if you meet the real thing your body can fight it off faster and more effectively. This does not always stop you catching flu or COVID altogether, but it greatly reduces the chance of becoming seriously ill, being admitted to hospital, or dying — which is the main goal, especially for vulnerable people. There is also a wider benefit: by making you less likely to catch and pass on the virus, vaccination helps protect those around you, including relatives who may be frail or unable to be vaccinated themselves. This combination of personal and community protection is why the NHS runs the programme every year and encourages take-up.

What to expect and side effects

Flu and COVID vaccines are usually quick and straightforward, given as an injection into the upper arm, or as a nasal spray for children's flu vaccine. It is often possible to have flu and COVID vaccines at the same visit, one in each arm, which is convenient and safe. Mild side effects are common and a sign the immune system is responding: a sore arm, tiredness, headache, aching muscles or a mild fever for a day or two. These usually settle quickly. Serious reactions are very rare, and staff giving the vaccines are trained to deal with them. You cannot catch flu from the injected flu vaccine, as it does not contain live virus. If you feel unwell for more than a couple of days, seek advice.

Making an informed choice

Deciding to have seasonal vaccines is a personal choice, and it helps to base it on reliable information rather than rumours online. The evidence shows these vaccines are safe and effective at reducing serious illness, and they are especially valuable for those at higher risk and the people who care for them. If you have questions or concerns — for example about allergies, being pregnant, or a health condition — your GP, practice nurse or pharmacist can give tailored advice. Vaccination is usually free and easy to arrange when you are eligible, often at a GP surgery or local pharmacy. This article is for education only and does not replace personal medical advice; if you are unsure whether a vaccine is right for you, ask a healthcare professional.