A booster shot against Covid-19 will be offered again this year. Two different vaccines and the question of the right timing make the decision difficult.
It’s Covid season again – and therefore time to think about a booster vaccination. Since the beginning of August, doctors’ offices and pharmacies have been able to order the updated Comirnaty vaccine from Biontech. But when? Because the peak of the wave may not come for another three months. Is now the right time – or is it worth waiting until it really gets going? And should only those for whom the STIKO recommends the booster really get vaccinated? This year, the question of the right vaccine is also a completely new one. While the manufacturer Biontech is relying on the virus variant JN.1 for the update, US manufacturers such as Moderna have made a different choice. The following overview should help with the vaccination decision.
What are the benefits of the booster vaccination?
Almost everyone in Germany now has a basic immunity against Covid-19, which means that severe cases have become much rarer. However, the disease is still by no means harmless. In addition to annoying but temporary infections, the virus still causes many hospital stays, unpleasant long-term consequences and thousands of deaths.
In 2023, there were around 16,000 in Germany. Above all, however, the protective effect of the vaccination decreases over time. According to a study published in May 2024, the 2023 booster prevented around half of all infections four weeks after vaccination, but after ten weeks the protection was only 33 percent.
What is crucial, however, is that protection against serious illness also weakens over time, albeit more slowly. After ten weeks, it had fallen from 67 to 57 percent in the study. It is not known exactly how much of this is left after a year – especially since completely different versions of the virus are now circulating. This year’s booster vaccination is better adapted to these newer versions.
Who should get vaccinated?
The booster vaccination increases protection against Covid-19 for a few months, especially against the newly circulating variants. That is why the booster is still useful for large parts of the population. Even the STIKO’s assessment, which is very restrictive by international standards, does not only provide for an annual booster vaccination for very old and seriously ill people.
The committee recommends the booster for all people over 60, for medical and nursing staff, and for people with an increased risk of severe disease and – what is easily forgotten – their relatives and close contacts. And this increased risk affects many people: in addition to cancer and immune deficiency, this includes chronic diseases of the liver, kidneys, respiratory tract, metabolism, cardiovascular system, but also mental and neurological diseases and severe obesity.
The STIKO recommendations are not the final answer to the question of who would benefit from the booster. “There are certainly other recommendations,” says Luka Cicin-Sain, head of the Department of Viral Immunology at the Helmholtz Centre for Infection Research (HZI). For example, the Centers for Disease Control and Prevention (CDC) in the USA recommends the booster just three months after the last infection, and for all people over the age of six months.
“This is a slightly different interpretation of the same study, but it is the same virus and the same vaccines,” he explains. “Of course, the risk is much higher for older people. But long Covid, for example, can also affect younger people.” It is absolutely plausible to assume that the protection against long Covid offered by the vaccination also decreases over time. “I think it is absolutely legitimate if young, healthy people also want to protect themselves.”
There are good arguments for booster vaccinations beyond the STIKO recommendation, especially for pregnant women and small children. According to various analyses, pregnant women have a higher risk of severe Covid-19 cases, and infection with Sars-CoV-2 simultaneously increases the risk of complications during birth.
In addition, newborns inherit antibodies from their mothers, so vaccinating pregnant women also protects the child in the first few months of life. The STIKO does not recommend vaccinating children because the disease is usually mild in them and most children have already been immunized by an infection during the pandemic. However, that is no guarantee, says Cicin-Sain.
“Covid-19 is currently about four times more dangerous than the flu. This is a clear argument for vaccinating children who were born since then and have not yet been infected before their first infection,” he explains. The STIKO also emphasizes that there are no safety concerns about vaccinating children.
When should you get vaccinated?
Protection is at its highest around two to four weeks after vaccination and then declines again. Accordingly, many people want to ensure that this phase coincides with the autumn Covid wave. If you vaccinate too early, protection may already be significantly reduced when you need it most.
In winter 2023/24, the peak of the Covid wave fell in mid-December – which would suggest vaccination in November. The problem: There are already quite a lot of infections, and becoming infected while waiting for the perfect moment to be vaccinated is annoying to say the least. In fact, however, the ideal time also depends on the individual risk profile and other factors: Anyone who has already been infected or vaccinated in the summer is initially sufficiently protected.
Anyone who is at high risk of becoming seriously ill should get the vaccination as soon as possible – the same applies if you have an exceptionally high number of contacts who may be ill. People with existing basic immunity and no risk factors can afford to wait longer. There may well be good reasons for postponing the vaccination. For example, if you are going on holiday, attending a conference or a similar event in November or December, it may be worth getting the vaccination four weeks beforehand in order to be optimally protected at the time in question.
Should you get the Covid-19 vaccine together with the flu vaccine?
It is also conceivable that you could take the opportunity to have the Covid vaccination done together with the flu vaccination. In principle, there is nothing wrong with getting both vaccines on the same day. However, there are certainly arguments in favor of doing the two separately.
The flu vaccination also only offers partial protection, which is at its highest around two to four weeks after vaccination and then decreases. And while a smaller Covid summer wave has been underway for weeks and will probably soon transition seamlessly into the autumn wave, there is no sign of the flu – and that will probably not change until mid-December.
This gives you a choice: If you get vaccinated now, your protection against the flu will wear off before it even becomes relevant. If you wait until October or November, you may become infected with Covid before you are vaccinated. Or you can make two vaccination appointments – one now and one in late autumn.
What is the difference between the different variant vaccines against Covid-19?
For the first time this year, there are vaccines that are effective against different variants of Sars-CoV-2. The already available Comirnaty vaccine is based on the JN.1 virus line, which dominated in Germany in January 2024 but no longer plays a role. Other manufacturers, such as Moderna, are following the recommendation of the US Food and Drug Administration (FDA) to use the newer KP.2 line. This virus version is a derivative of JN.1 that emerged in the summer.
“If both are equally available, the newer version KP.2 is preferable,” says Luka Cicin-Sain. However, the virus is constantly evolving, and it is unclear whether there is really any benefit in waiting for the KP.2 vaccine.
“Currently, the KP.3.1.1 variant seems to predominate, but the recombinant XEC variant is also becoming increasingly common. It is very difficult to predict where this journey will take us.” In addition, the Robert Koch Institute pointed out in response to a request from Spektrum that the two variants only differ in three mutations in the spike protein. It can be assumed that both provide comparable levels of protection.
