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How effective are the COVID-19 vaccines? How long do they protect against COVID-19 infection?

The efficacy of existing vaccines against other diseases is not always the same in everyone. Studies show that the effectiveness of the available COVID-19 vaccine from AstraZeneca is about 79,0% (after 2 doses) and from Johnson & Johnsons about 66.3% (after 1 dose). Earlier studies show that the efficacy of the mRNA COVID-19 vaccines (Pfizer and Moderna) is between 90% and 95% (after 2 doses). For example, an efficacy of 90% means that if 100 people are vaccinated, 90 are effectively protected against the virus. Even if the vaccine does not offer 100% protection and the vaccinated person becomes ill, the symptoms are usually less severe and the course of the illness shorter.

We still do not know exactly how long the protection of COVID-19 vaccines lasts, but current evidence suggests that most people have high protection against serious illness and death for at least six months. Immunity may decline more rapidly in people who are older or who have underlying medical conditions, or who have had high exposure to the virus. To protect yourself, get vaccinated AND continue to follow the other protective measures against COVID-19 such as social distancing and wearing a mask when in public. Because research shows that protection decreases 6 months after initial vaccination, the Superior Health Council recommends that everyone over the age of 18 receive a booster vaccine. From now on, a booster vaccine is also offered to young people aged 12 and above (informed consent of parents or guardians is required for vaccination of young people under 18 years of age).

Generally, the following periods apply between the last dose and the booster dose:

  • Pfizer and Moderna: 4 months after last shot (with Pfizer or Moderna COVID-19 vaccine)
  • AstraZeneca: 4 months after last shot (with Pfizer or Moderna COVID-19 vaccine)
  • Johnson & Johnson: 2 months after last shot (with Pfizer or Moderna COVID-19 vaccine)

In Belgium, only the Pfizer or Moderna COVID-19 vaccine is used as booster vaccine. The different COVID-19 vaccines may be combined.