What are the common side effects of vaccines? What factors may affect the quality of vaccines and lead to adverse events after vaccination?
Mild Reactions
 |
| The joy of the treating physician when one of the two children recovers from a critical condition (Photo: VNE) |
Dr. Tran Tinh Hien, Deputy Director of Ho Chi Minh City Tropical Disease Hospital, stated that when adverse reactions occur following vaccination, the cause may fall into one of two categories: related to the vaccine itself or due to a flaw in the vaccination process.
According to Dr. Tinh Hien, no biological product or pharmaceutical can be produced with 100% absolute safety and effectiveness. Attempting to produce a vaccine with complete safety may compromise its efficacy.
Currently, with existing technology, vaccine manufacturers strive to produce formulations with the highest possible safety and efficacy. However, rare adverse reactions still occur. Common mild side effects of certain vaccines include localized reactions (pain, swelling, redness), fever, discomfort, irritability, and occasionally diarrhea and headaches.
Localized reactions typically arise about 1-2 days after vaccination, except for fever and systemic symptoms associated with measles or measles-mumps-rubella vaccines, which can occur from 5-12 days post-vaccination.
A vaccine is considered effective when it has few side effects and high efficacy. Localized reactions such as pain, swelling, or redness at the injection site occur in approximately 10% of vaccinated individuals. Fever also occurs in about 10% or less. The Diphtheria-Pertussis-Tetanus (DPT) vaccine has a higher rate of side effects, potentially affecting up to 50% of those vaccinated.
Vaccination Errors
Dr. Tinh Hien noted that errors during vaccination can also occur and may lead to severe reactions.
Specifically, if vaccination is not performed under sterile techniques, such as reusing syringes or needles, or if disinfecting syringes and needles is not done correctly, or if the vaccine is contaminated, complications like abscesses at the injection site, bloodstream infections, toxic shock, and even death can occur, potentially spreading hepatitis viruses or HIV. If errors occur in vaccine preparation, such as not properly shaking the vaccine, using incorrect diluents, or reusing diluents, this can lead to local abscesses, loss of vaccine efficacy, or death.
Errors in choosing the injection site, such as BCG being injected subcutaneously or DPT being injected too superficially or into the buttocks, can cause reactions or abscesses. If transport errors occur, the vaccine may lose its effectiveness. Additionally, failing to respect contraindications may result in severe reactions.
Most adverse reactions are mild and easily treatable, without lasting consequences. Severe reactions occur at a very low rate (1 in 1,000,000).
Improper Storage
Pharmacist Do Tuong Phuoc, Scientific Director of Sanofi Pasteur Vietnam, further explained that according to regulations, common vaccines must be stored at the correct temperature of 2-8°C. However, there are special cases, such as the polio vaccine, which must be stored at -20°C. This is a mandatory regulation that must be strictly followed.
If a vaccine is kept outside the recommended storage temperature, WHO recommends retesting the vaccine for quality. If it is still effective, it should be used as soon as possible. If it does not meet quality standards, it must be disposed of properly.
When a vaccine freezes, it forms precipitates, which can cause swelling and abscesses at the injection site when administered. If a vaccine is exposed to temperatures higher than permitted, in certain special circumstances, a “live” vaccine instead of a killed virus may be warmed and become viable again, which could turn it into a pathogenic virus for the body.
LE THANH HA
Adverse Events: More Than One in a Million? According to GlaxoSmithKline, the Priorix™ vaccine is generally safe and has been used in millions of children worldwide. This is true, but I want to point out that adverse reactions to similar vaccines produced by Merck have been reported in medical literature, and the rate of adverse reactions is not lower than one in a million vaccinations, as some have suggested. According to an epidemiological study published in 2000, of 1.8 million vaccinated individuals, there were 437 reported cases of vaccine adverse effects, of which 137 cases were considered life-threatening due to the vaccine. Among these was a 13-month-old boy who died eight days after receiving the vaccine. The cause of this death remains unclear but may not be related to the vaccine. The remaining cases included serious adverse effects such as asthma, seizures, meningitis, and pneumonia… In this study, besides those “dangerous” cases, many mild adverse reactions were also reported, such as fever (180 cases), rashes (132 cases), lymphadenopathy (69 cases), and rhinitis (37 cases)… Most cases of vaccine reactions occurred at two time points: within 24 hours, or 7-10 days after vaccination. Prof. Nguyen Van Tuan – Garvan Institute of Medical Research, Sydney, Australia (ykhoa.net) |
