What are the risks associated with vaccinated children?

From the Guidelines

Vaccinated children are at risk of experiencing mild to moderate adverse reactions, including fever and febrile seizures. Specifically, children who receive the MMR vaccine may experience a low-grade fever and rash, while those who receive the MMRV vaccine may be at a higher risk for febrile seizures during the 5-12 days after the first dose, with an estimated one additional febrile seizure per 2,300-2,600 children vaccinated 1. Additionally, children who receive the influenza vaccine may experience local reactions, such as pain, redness, and swelling at the injection site, as well as systemic reactions like fever, fatigue, and headache 1.

• The most common adverse events after IIV3 administration are local injection site pain and tenderness, with fever occurring within 24 hours after immunization in approximately 10% to 35% of children younger than 2 years 1.
• Febrile seizures have been reported in children who received IIV3 and PCV13 concomitantly, with a slight increase in the risk of febrile seizures in children 6 through 23 months of age 1.
• The MMRV vaccine has been associated with a higher risk of febrile seizures compared to the MMR vaccine and varicella vaccine administered separately, particularly in children aged 12-23 months 1.
• The benefits of timely vaccination with same-day administration of IIV and PCV outweigh the risk of febrile seizures, which rarely have any long-term sequelae 1.

It is essential to note that the risks associated with vaccination are generally mild and temporary, and the benefits of vaccination in preventing serious diseases far outweigh the risks. Parents and caregivers should discuss the risks and benefits of vaccination with their healthcare provider to make informed decisions about their child's health.

From the FDA Drug Label

There is a risk of fever and associated febrile seizure in the first 2 weeks following immunization with M-M-R II vaccine. For children who have experienced a previous febrile seizure (from any cause) and those with a family history of febrile seizures there is a small increase in risk of febrile seizure following receipt of M-M-R II vaccine Transient thrombocytopenia has been reported within 4-6 weeks following vaccination with measles, mumps and rubella vaccine. The following adverse reactions include those identified during clinical trials or reported during post-approval use of M-M-R II vaccine or its individual components. Body as a Whole Panniculitis; atypical measles; fever; headache; dizziness; malaise; irritability. Cardiovascular System Vasculitis. Digestive System Pancreatitis; diarrhea; vomiting; parotitis; nausea Hematologic and Lymphatic Systems Thrombocytopenia; purpura; regional lymphadenopathy; leukocytosis. Immune System Anaphylaxis, anaphylactoid reactions, angioedema (including peripheral or facial edema) and bronchial spasm. Musculoskeletal System Arthritis; arthralgia; myalgia Nervous System Encephalitis; encephalopathy; measles inclusion body encephalitis (MIBE) subacute sclerosing panencephalitis (SSPE); Guillain-Barré Syndrome (GBS); acute disseminated encephalomyelitis (ADEM); transverse myelitis; febrile convulsions; afebrile convulsions or seizures; ataxia; polyneuritis; polyneuropathy; ocular palsies; paresthesia; syncope Respiratory System Pneumonia; pneumonitis; sore throat; cough; rhinitis. Skin Stevens-Johnson syndrome; acute hemorrhagic edema of infancy; Henoch-Schönlein purpura; erythema multiforme; urticaria; rash; measles-like rash; pruritus; injection site reactions (pain, erythema, swelling and vesiculation).

The risks associated with vaccinated children include:

• Febrile seizure: a risk of fever and associated febrile seizure in the first 2 weeks following immunization
• Thrombocytopenia: transient thrombocytopenia has been reported within 4-6 weeks following vaccination
• Anaphylaxis: anaphylaxis, anaphylactoid reactions, angioedema, and bronchial spasm
• Neurological reactions: encephalitis, encephalopathy, measles inclusion body encephalitis, subacute sclerosing panencephalitis, Guillain-Barré Syndrome, acute disseminated encephalomyelitis, transverse myelitis, febrile convulsions, afebrile convulsions or seizures
• Other reactions: pancreatitis, diarrhea, vomiting, parotitis, nausea, arthritis, arthralgia, myalgia, pneumonia, pneumonitis, sore throat, cough, rhinitis, Stevens-Johnson syndrome, acute hemorrhagic edema of infancy, Henoch-Schönlein purpura, erythema multiforme, urticaria, rash, measles-like rash, pruritus, injection site reactions 2 2

From the Research

Risks Associated with Vaccinated Children

The risks associated with vaccinated children can be categorized into several types, including:

• Local reactions, such as pain, swelling, and redness at the injection site 3, 4, 5
• Systemic reactions, such as fever, fatigue, and headache 4, 5
• Serious adverse events, such as anaphylaxis, Guillain-Barré syndrome, and seizures 3, 4, 6
• Rare adverse events, such as Arthus reaction, which is a type of hypersensitivity reaction that can occur after vaccination 3

Adverse Reaction Rates

The rates of adverse reactions to vaccines in children vary depending on the vaccine and the population being studied. For example:

• A study of the Pfizer-BioNTech COVID-19 vaccine in children aged 5-11 years found that approximately 8.7 million doses were administered, resulting in 4,249 reports of adverse events, of which 4,149 (97.6%) were not serious 4
• A study of the safety of vaccines used for routine immunization in the United States found that the vast majority of studies either did not investigate or could not identify risk factors for adverse events associated with vaccination 6
• A study of the incidence of adverse reactions to vaccines in a pediatric population found that 191 non-serious suspected adverse reactions were detected, representing 19% of the vaccinated children 5

Vaccine-Specific Risks

Some vaccines have been associated with specific risks, including:

• Measles, mumps, and rubella (MMR) vaccine and febrile seizures in children under age 5 6
• Varicella vaccine and disseminated Oka strain varicella zoster virus with associated complications in individuals with demonstrated immunodeficiencies 6
• Rotavirus vaccines and intussusception in children 6
• COVID-19 vaccine and local injection site reaction, fatigue, and headache 4, 7

Special Populations

Certain populations, such as children with a history of multisystem inflammatory syndrome in children (MIS-C) or COVID-19, may be at increased risk for adverse events after vaccination. However, studies have found that COVID-19 vaccination is well tolerated in these populations 7