The Ministry of Health periodically publishes the Pharmacovigilance Report about COVID-19 vaccines. The report aims to communicate the adverse reactions that are producing the vaccines against the coronavirus. In its fourteenth update, the document makes special mention of the third dosesthat is, the booster vaccines from Pfizer and Moderna, also known as Comirnaty and Spikevax, respectively.
According to data from the Ministry of Health, 92.5% of people over 12 years of age have already received the full guideline against COVID-19. Besides, A total of 24,639,562 additional doses have already been applied. In Spain, only those that use messenger RNA technology, that is, Pfizer and Moderna, are injected as third doses.
In the case of Pfizer, Almost 11 million booster doses have been administered, specifically 10,913,320 punctures. It is the most widely used vaccine in Spain, but in terms of the use of third doses, it is not the most widely used, since more than 13 million additional doses of the Moderna vaccine have been supplied.
Adverse effects of third doses of Pfizer
The pharmacovigilance report collects the ten most reported adverse effects of the Pfizer vaccineas well as its percentage with respect to the total number of notifications identified for the third dose.
The most common adverse effect was lymphadenopathy, that is, swollen lymph nodes (21% of those who had one experienced lymphadenopathy). The pirexia or fever was the second most recorded effect (20%), followed by headache or headache (10%). Below are the ten most common side effects from highest to lowest for the third dose of Pfizer.
The ten most common adverse effects of the third dose of Pfizer from highest to lowest
| Reaction (PT) | number of cases | Percentage |
| lymphadenopathy | 94 | 21% |
| Pirexia | 89 | 20% |
| Headache | 44 | 10% |
| Myalgia | 34 | 8% |
| Discomfort | 32 | 7% |
| Fatigue | 25 | 6% |
| Vaccination site pain | 19 | 4% |
| Shaking chills | 18 | 4% |
| Arthralgia | 15 | 3% |
| Axillary pain | 15 | 3% |
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