Differences between Pfizer and Moderna: side effects, effectiveness and time between doses

The Pfizer and Moderna vaccines are the only ones licensed for people under 40. In addition, both are also the only ones that can be used to immunize children under 12 years of age. Thus, it is appropriate to remember what effectiveness or side effects they have. The time between doses is 21 days for Pfizer and 28 for Moderna.

Effectiveness of the Pfizer and Moderna vaccine

The Pfizer and Moderna vaccines, both messenger RNA-based, offer 100% effectiveness against developing severe disease. However, neither prevents infection. For this reason, those vaccinated must continue to respect prevention measures such as the safety distance or the mask.

Against the development of symptoms, Pfizer’s effectiveness is 95% and Moderna’s is 94.1%. However, this effectiveness drops to 88% for Pfizer, according to studies by Public Health England, compared to the Delta variant.

Side effects of the Pfizer and Moderna vaccine

1. The most frequent and common. The seventh pharmacovigilance report of the Spanish Agency for Medicines and Health Products (AEMPS) revealed the following adverse reactions: feverish state (37%), headache (27%), muscle pain (2o%), pain in the vaccination (14%), malaise (12%), nausea (8%), arthralgia (8%), chills (8%), fatigue (8%), lymphadenopathy (7%).

2. New or suspected side effects: during the application of the Pfizer vaccine in the general population, new side effects have been detected, some are already listed in the vaccine package insert and others are suspected:

– Skin rash and pruritus: Pfizer’s vaccine information sheet and package insert already contain skin rash and pruritus (skin itching), as uncommon adverse reactions (occurring in less than 1 in 100 people). For their part, urticaria (raised, red, itchy skin rash) and angioedema (rapid swelling under the skin) have been updated as adverse reactions that occur rarely (in less than 1 in 1,000 people).

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– Localized swelling with Pfizer in people who have previously received injections of dermal fillers in the face: the EMA has also concluded that this effect may be related to the vaccine, so it will be included as a possible adverse reaction in the data sheet and the prospect.

– Myocarditis and pericarditis: The EMA has concluded that myocarditis and/or pericarditis may very rarely occur after administration of BioNTech/Pfizer vaccines.

Moderna Vaccine Side Effects

1. The most common side effects. The seventh AEMPS pharmacovigilance report revealed the following: feverish state (50%), headache (30%), muscle aches (25%), pain in the vaccination area (19%), chills (11%) , malaise (13%), nausea (9%), arthralgia (8%), asthenia (6%).

2. New or suspected side effects. The latest AEMPS report also reveals a series of new adverse reactions such as: diarrhea and immune thrombocytopenia, which produces bruising and bleeding. Another side effect, which is also included in the latest update of the Spanish vaccination strategy, is a series of late skin reactions near the injection site that occur about 7 days (between 2 and 12 days) after receiving the vaccine. Likewise, the EMA has also collected myocarditis and pericarditis.

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