The next outbreak of the ‘100 day cough’

The 100 day cough is whooping cough, or pertussis to give it its proper name. Case numbers peak every 4 years generally. There was quite a big surge that peaked in 2012 in England. There was a smaller peak in 2016 and the next expected peak would have come in 2020. But nothing happened because the Covid lock-down nipped it in the bud.

The bar chart below is published by the UK Health Protection Agency and shows the startling drop in numbers from about 1000 per quarter to about 100. A 90% drop.

The same agency publishes weekly figures which are up to date (March 2023) and are still running at the same low level.

There can be little doubt that the isolation measures that were probably partly effective for Covid were highly effective in breaking the transmission of whooping cough.

This is good news in the sense that many people will have avoided getting the disease, which can be unpleasant for adults and very serious for babies.

Babies and pregnant mothers are routinely given pertussis immunisation, which is highly effective in those early years when it can be very nasty.

But outbreaks occur in spite of immunisation because it wears off after a few years. However, everyone’s immunity gets boosted thereafter by contact with the bacteria which constantly circulate widely and do their boosting without causing noticeable symptoms in most of the population.

One has to wonder if the lack of circulating pertussis bacteria, if the chart is really telling us that, means that that regular boosting has not been happening in parallel with the recognised cases.

I think we can expect a rather large surge in cases as a catch up when it eventually happens.

So make sure infants and children are fully up to date with their immunisations, and shout out to pregnant women to get their pertussis booster well before the baby is born.

Bar chart of pertussis cases showing sudden drop in 2020
Pertussis cases 2011 to 2022 in England


Retired GP who is an expert on clinical whooping cough

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