7.5.2 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?
[You learnt about herd immunity in Study Session 1.] 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.
7.5.1 Mild reactions to vaccines