The established practice in Norway is to observe everyone who has received a vaccine for 20 minutes. Is the observation necessary and is it cost-effective? I believe that an observation period of ten minutes is sufficient if there is no additional risk.
The Norwegian Institute of Public Health recommends a 20-minute observation period for everyone after vaccination (1). This practice is largely followed at all sites in Norway where vaccines are administered, even though it is not mandated by any Norwegian law or regulation. Neither is it mentioned in the precautionary rules for vaccination in the Norwegian Pharmaceutical Product Compendium. A Google search shows that a 15-minute observation period is standard in many countries, and in Sweden no observation period is recommended if there is no additional risk. When mass vaccination to combat COVID-19 started, the UK dropped the 15-minute observation period in order to speed up the vaccine rollout (2).
Anaphylactic reactions are potentially fatal but are extremely rare after vaccination. In Norway, seven deaths were reported as a result of an anaphylactic reaction to vaccination in the period 2011–20 (information from the Adverse Reactions Register). The cases are reported based on suspicion, and the explanation for this figure is unknown. Some may have died from other causes soon after vaccination, as was seen during the mass vaccination of older people at the start of the COVID-19 pandemic. In a US study, 33 cases of anaphylaxis were found after 25 million vaccine doses (1.3 per million), and there were no deaths. Twenty-six of the patients had at least one known predisposing factor (known allergy, allergic rhinoconjunctivitis, asthma or atopy). The onset of symptoms took place within 30 minutes in just eight of these cases, i.e. one per 3.1 million vaccine doses (3).
However, it is not possible to observe everyone long enough to be 100 % sure that no one has a vasovagal or anaphylactic reaction after leaving the vaccination clinic
In 2022, the average monthly salary in Norway was NOK 53 150 (4). If time is money, then ten minutes corresponds to NOK 55. If the patients are observed for twenty minutes instead of ten minutes, the price to prevent one person from having an anaphylactic reaction after leaving the vaccination clinic is therefore NOK 170 million, even if we were to assume that everyone who has the reaction in the first 30 minutes has it 10–20 minutes after vaccination.
It is not unusual for people to feel unwell before, during or immediately after vaccination, as part of a harmless psychological reaction that produces vasovagal symptoms. This in itself is a good reason to observe the patients. In a study from 1997, 697 cases of fainting after vaccination were reported, of which 88.8 % occurred within 15 minutes (5).
Patients who have previously had an anaphylactic reaction to an egg-based vaccine will not usually be given a new egg-cultured vaccine. If it relates to a mandatory vaccine to protect against yellow fever, they will be issued with an exemption certificate. It may be justifiable to administer the vaccine in a hospital outpatient clinic if a peripheral venous catheter is inserted before vaccination. Then an observation period of at least 60 minutes is recommended (6).
However, it is not possible to observe everyone long enough to be 100 % sure that no one has a vasovagal or anaphylactic reaction after leaving the vaccination clinic. My suggestion is that anyone with a confirmed or suspected allergy (allergic rhinoconjunctivitis, asthma, urticaria or atopy) should wait at least 20 minutes after the last vaccine dose. Those who become unwell after vaccination must be observed until they feel well. Others who feel well when they are ready to leave may be allowed to go if at least ten minutes has passed since the last vaccine was administered.