Title: Serious vaccine reactions
Course: Immunization - Ethiopia (Full)

Serious vaccine reactions

On rare occasions, a reaction to a particular vaccine can be serious, even so serious as to be life-threatening. When serious problems follow an immunization, rumours are likely to circulate in the community that immunization is not safe, and children may then not be brought by parents for immunization. This will have a damaging effect on the spread of infectious diseases in the community.

Can you explain why a measles epidemic is likely to occur in a community if not enough children receive measles vaccine?

Show answer

The reason is because the herd immunity in the population will be too low to prevent the measles viruses from spreading; it can pass from infected children to the many susceptible children who have not be immunized.

Table 7.2 summarises the possible serious adverse reactions to different vaccines that you may very rarely encounter. For example, acute flaccid paralysis following OPV occurs about once in every 1–10 million children vaccinated.

Vaccine | Serious adverse event | Estimated period of onset time after immunization
BCG | Abscess (collection of pus) | 1–6 weeks
Swollen lymph nodes in the armpit | 2–6 months
Bone disease | 1–12 months
Pentavalent or DPT | Severe acute allergic reaction | 0–1 hour
Continuous screaming | 0–24 hours
Brain disease, seizures (convulsions, fits) | 0–3 days
Abscess | 1–6 weeks
HepB | Severe acute allergic reaction | 0–1 hour
Paralysis | 1–6 weeks
Measles | Severe acute allergic reaction | 0–1 hour
 | Abscess | 1–6 weeks
OPV | Acute flaccid paralysis | 4–30 days
TT (women) | Severe acute allergic reaction | 0–1 hour
Nerve damage in the arm | 2–28 days

However, most adverse events following immunization are not due to reactions caused by the vaccine. We will look at the other causes of AEFIs next.