The Spanish vaccination strategy is focused on the immunization of those under 40 years of age, a group that is mainly receiving Pfizer, because many more doses are arriving than Moderna, the only other vaccine authorized for this age group. However, that difference is expected to narrow for the remainder of the summer. Thus, it is timely to remember the most frequent and new side effects of the Moderna vaccine against Covid-19.
Side effects of Moderna are mostly reported by women
The sixth pharmacovigilance report of the Spanish Agency for Medicines and Health Products (AEMPS) reveals that until May 30, 2021, the FEDRA system (Spanish Pharmacovigilance data on suspected adverse reactions) has registered a total of 2,850 notifications of Adverse events after administration of the vaccine. Of these, 374 were considered serious. In addition, the majority of cases correspond to women (82%) and people between 18 and 65 years old (89%).
The most common side effects of Moderna
The AEMPS report also shows the 10 most notified adverse events, as well as their percentage with respect to the total number of registered notifications. All of them, except malaise and asthenia (symptoms that could be caused by other events such as fever), constitute known adverse reactions for this vaccine and are already included in its technical data sheet and package insert.
– Fever: 50%
– Headache: 32%
– Muscle pain: 24%
– Pain in the vaccination area: 18%
– General malaise: 12%
– Chills: 12%
– Nausea: 10%
– Fatigue: 9%
– Joint pain: 9%
– Asthenia: 6%
New or suspected side effects of the Moderna vaccine
Since the administration of the Moderna vaccine in the general population, new side effects have emerged, which have been evaluated by the European Pharmacovigilance Committee (PRAC), dependent on the European Medicines Agency (EMA).
1. Diarrhoea: Based on the available cases, the PRAC has identified diarrhea as a new adverse reaction that may occur with the vaccine.
2. Delayed reactions at the injection site. Delayed local reactions may appear several days after receiving the vaccine and should not be confused with cellulitis.
3. Immune thrombocytopenia. The PRAC suspects this autoimmune disorder that causes low levels of platelets in the blood, leading to bruising and bleeding. .
4. Myocarditis and pericarditis. PRAC has recommended including myocarditis and pericarditis as new side effects in Moderna’s product information. However, it clarifies that it is a rare adverse reaction.