Why do some people develop better protection after vaccination than others?
How well you respond to a vaccine depends on your genetic predisposition, age, the condition of your immune system, and any medications or diseases you may have. If you use immunosuppressive medication such as rituximab, discuss with your doctor whether additional measures are needed.
Genetic predisposition is the most important explanation for the variation in how well people respond to vaccines. The so-called HLA system, the set of proteins your body uses to recognise vaccine substances and present them to the immune system, differs from person to person. Certain variants of this system are associated with a weaker response. This means some people are naturally less amenable to protection through vaccination, regardless of which vaccine is used.
The state of your immune system just before vaccination also plays a role. Research into the BCG vaccine showed that people with a relatively quiet immune system benefited more from it than people whose system was already active. Genetic and environmental influences on which genes are switched on or off predicted that difference. Universally benefiting from a vaccine is therefore not a given: the starting position matters.
Age is a third factor. Older people respond on average less strongly to vaccines than younger adults, and they also vary much more among themselves. This makes it harder to give standard recommendations: group averages mask the fact that one person at an advanced age still responds well while another barely responds at all.
Certain diseases and medications substantially suppress the vaccine response. People with multiple sclerosis who use rituximab or fingolimod produced far fewer antibodies after COVID-19 vaccination than MS patients on other medications. Coeliac disease is also associated with a poorer antibody response to the hepatitis B vaccine, while the response to other vaccines in children with this condition largely remains comparable to that of healthy children. COPD likewise leads to a less reliable flu vaccine effect, although the evidence for this is more limited.
On the positive side: people who had previously had COVID-19 and were subsequently vaccinated responded more strongly than those who had only been vaccinated. This so-called hybrid immunity produced higher antibody levels and stronger T-cell responses. Vaccines containing adjuvants, substances that additionally activate the immune system, can also boost the response in people with a less favourable predisposition, although individual differences remain.
All claims are based on PMIDs 28566880, 38198850, 23953808, 38898409, 35710573, 26378476, 37673427 and 30043342. Most studies are observational or small-scale; causal relationships are most strongly supported for genetics and medications. The evidence is thinnest for COPD.
Which vaccinations belong to healthy ageing?
For healthy ageing, the flu vaccine (high dose), the pneumococcal vaccine, the shingles vaccine, and the RSV vaccine are well supported for people aged 60 and older; discuss which ones you are still missing with your GP or pharmacist.
Does spending more time outdoors help your immune system as you get older?
Spending more time outdoors may support your immune system as you get older, mainly through improved vitamin D production, but whether this actually leads to less illness has not yet been conclusively demonstrated. How polluted the outdoor air is also matters: in areas with serious air pollution, being outside can in fact be detrimental.
Can you strengthen your immune system by eating more fibre?
Eating more fibre has a clear biological mechanism, but in healthy people it does not automatically lead to a measurably stronger immune system. Fermented foods appear to work more reliably for your gut microbiome; probiotic supplements are even risky when used alongside immunotherapy.
Does exercise help your immune system as you age?
Regular, moderate exercise helps your immune system by reducing smouldering inflammation. Suddenly training very hard without a gradual build-up can actually temporarily lower your immune defences.
Why do older adults become seriously ill from an infection more quickly?
Ageing weakens the immune system in several ways simultaneously, making infections more dangerous. Keep vaccinations up to date and discuss nutritional deficiencies with your doctor, as these additionally increase vulnerability.
Does eating enough protein help my immune system as I get older?
Eating enough protein helps your immune system in later life. Aim for at least 1.0-1.2 grams per kilogram of body weight per day, spread across your meals, and preferably obtain this from ordinary food rather than supplements.