COVID-19 vaccines for adults

The vaccines differ in their ingredients and how they activate the immune system:

• mRNA vaccines: mRNA vaccines contain the “blueprint” (copy of a gene) for a protein on the surface of the SARS-CoV-2 coronavirus. This blueprint in the vaccine enters the body’s cells in tiny fat particles (lipid nanoparticles). The cells then make that typical coronavirus protein (spike protein) for a short time. The immune system reacts to the protein, making antibodies and special cells to fight it. The blueprint is then broken down in the cells.
• Vector vaccines: Vector vaccines are made from the “shells” of harmless viruses that also contain the blueprint for a protein on the surface of the SARS-CoV-2 coronavirus. These vectors are absorbed by body cells that then make the spike protein for a short time.
• Protein-based vaccine: The protein-based vaccines contain coronavirus-like particles with the typical spike protein on them. The spike protein in these vaccines is made in a lab and injected directly.
• Inactivated vaccine: These "killed" vaccines (inactivated and adjuvanted whole-virus vaccines) contain dead parts of the SARS-CoV-2 virus. They also contain substances known as adjuvants, which improve the immune response.

The Comirnaty and Spikevax vaccines have been adapted to provide more protection specifically against the omicron variant of the virus.

COVID-19 vaccines can reduce the risk of catching the virus and becoming ill. But this protection against an infection with symptoms is limited, and hardly there anymore after a few months. Then you may get infected with the virus and have symptoms despite being vaccinated (known as a “breakthrough infection”). Most people then have symptoms like a cough or sore throat.

But the vaccination is very good at preventing severe COVID-19 illness. That protection is probably more long-term in most people. The long-term immune memory then stops COVID-19 infections from spreading from the upper airways to the lungs and other organs. In certain groups of people, though, that protection against severe illness can decrease after a few months (for instance, in older people and those with weakened immune systems). But it can be refreshed again with booster vaccinations.

Similar to when you're vaccinated, when you recover from a COVID-19 infection the immune system makes immune cells that can help stop you from getting COVID-19 again and prevent severe illness if you do.

It is normal for vaccinations to have certain side effects. That can be a sign that your body is reacting to the vaccine and starting to build immunity (protection).

Depending on the vaccine, the following reactions occur in 70 to 90% of vaccinated people:

• Reactions where the needle went in, including pain, reddening or swelling
• Physical symptoms such as fever, chills, headache, aching muscles and joint pain

These reactions to a vaccine are usually mild and go away again within a few days.

All vaccines can cause an immediate allergic response (anaphylactic reaction) that usually has no lasting effects. That is very rare, though, occurring in fewer than 1 in 100,000 vaccinations.

In very rare cases, mRNA vaccines and vector vaccines have been observed to cause the following complications, some of which may also lead to long-term problems:

In certain groups of people, the risk of myocarditis and pericarditis may be higher in the first few days after an mRNA vaccine (Spikevax or Comirnaty). This mainly affects male teenagers and young men after having the second dose of the vaccine. According to the European Medicines Agency (EMA), it occurs in up to 1 out of 10,000 people (Comirnaty). The risk is slightly higher with Spikevax (up to 2 out of 10,000 people), so Spikevax is no longer recommended for people aged between 12 and 30.

It is important to see a doctor soon if the following symptoms occur in the first few weeks after vaccination:

• Chest pain
• Shortness of breath
• Unusual racing heart or palpitations

In very rare cases, people developed blood clots in unusual places after vaccination with Vaxzevria or Jcovden. These included veins in the head (cerebral venous sinus thrombosis) and the belly (splanchnic vein thrombosis). The number of blood platelets (thrombocytes) in the blood is also often abnormally low.

According to the European Medicines Agency (EMA), these complications occur in less than 1 out of 10,000 people. Because of this, vector vaccines are now only recommended for people aged over 60. Vaxzevria is no longer available in Germany.

If any of the following symptoms develop within three weeks of vaccination, you should see a doctor soon and tell them about the vaccination:

• Breathing problems
• Pain in the chest or stomach
• Swelling in one leg
• Severe or increasingly bad headaches, or blurred vision
• Several small bruises, reddish or purple patches, or blood blisters beneath the skin

The safety of the vaccines is monitored by international authorities. In Germany, the Paul Ehrlich Institute publishes safety reports on vaccines.

Please note that some of the following information describes the situation in Germany specifically. You may find that things are different elsewhere.

The German Standing Committee on Vaccination (STIKO) recommends yearly boosters for the following groups of people:

• Everyone aged 60 and over
• People who are living in care homes
• People aged 6 months and over who have underlying medical conditions that increase the risk of COVID-19 making them very ill
• People aged 6 months and over who have underlying medical conditions that increase the risk of COVID-19 making them very ill
• Staff in medical facilities who have contact with patients

The yearly boosters should generally be given at least 12 months after the last vaccination or a previous infection. It is best to have booster shots in the autumn because the infection rates are highest in the autumn and winter.

People with a weakened immune system can already have another vaccination sooner. This decision is made together with their doctors.

According to the STIKO, three COVID-19 vaccines are enough to stop healthy people under the age of 60 (including pregnant women) becoming seriously ill from the virus over the long term. They are also believed to have enough protection if they have had two vaccines and recovered from an infection, for example.

mRNA vaccines (Comirnaty or Spikevax) are usually recommended for booster vaccinations. If possible, you should use the same mRNA vaccine that was used for the first vaccination. For people under 30, the STIKO now only recommends the Comirnaty vaccine. Sometimes there are medical reasons for not being vaccinated with Comirnaty or Spikevax. Then Nuvaxovid can be used instead.

The VidPrevtyn Beta vaccine has only been approved for booster vaccinations. But the STIKO doesn't recommend using it.

Booster vaccinations can cause the same typical short-term reactions described above, such as pain where the needle went in, a headache, tiredness or fever. According to the STIKO, there is no evidence to suggest that booster vaccinations cause different complications than the first vaccinations might.

According to the STIKO, there is no good reason to test for coronavirus antibodies before having a booster. The level of protection offered by antibodies can vary from person to person and doesn't only depend on the amount of antibodies in the blood. And our bodies have other "weapons" to fight the virus with (not only antibodies). So your antibody count can't reliably predict how well you're protected from COVID-19.

If people still have symptoms more than four weeks after a COVID-19 infection, they are considered to have long COVID. If the symptoms still haven't gone away after more than twelve weeks, it is called post COVID. These longer-lasting symptoms mainly include exhaustion, shortness of breath and difficulty concentrating. There is a lack of research on how well vaccinations can prevent long COVID and post COVID. But the available studies suggest that they reduce the risk of longer-term symptoms.