Keyworth Health Centre serves a discrete community 6 miles south of Nottingham, England. This medical practice under the leadership of general practitioner Dr Doug Jenkinson (myself) has recorded all detectable cases of whooping cough (based on a minimum of 3 weeks of paroxysmal coughing) since 1977. I retired in 2011 and was able to continue to gather figures until 2013. My ability to personally monitor practice cases has ceased. The figures provide a unique set of data about this important disease, that compliments official statistics and provides an alternative perspective.
Clinical diagnosis made on the basis of at least 3 weeks of paroxysmal coughing. This is unchanged since the study began. If a positive swab or positive blood test were found and there was less than 3 weeks of paroxysmal coughing, it would be excluded from the study total. There have been about 3 such instances.
The study in more detail.
The general medical practice at Keyworth Health Centre in Nottinghamshire, England, is the only practice covering Keyworth, Tollerton and some surrounding villages. The practice population has been roughly 11,000 since 1970. In 1977 there was an outbreak of whooping cough which occurred following a massive drop (from 80% to 31%) in the national immunisation rate. It was possible to calculate from this small outbreak affecting 191 people (126 under 5), the vaccine protection rate in the under fives (84%), as efficacy had been called into question. The conclusion was that the vaccine appeared as effective as had been thought (about 80%) and the results were published in the British Medical Journal.
Because of the relative ease of detecting clinically diagnoseable whooping cough in a small discrete practice with enthusiastic staff, I continued recording as much detail as I could of all cases I subsequently could find. Whenever practicable, pernasal swabs were taken for pertussis, and the positive culture rate confirmed we were diagnosing correctly. Since 2002 we have been able to do a blood test for pertussis toxin IgG and the results of these continue to support the validity of our clinical diagnosis.
I have written several papers as a result of this study, which now numbers over 728 cases. Four of these have been in the BMJ. I have watched the number of cases remain steady for 25 years, while the number of notifications has dropped to under 600 per year (changed 2011-12). I became very concerned about the lack of awareness of whooping cough and its features among doctors and nurses. So in 2000 I set up a website (the parent of this one this one, www. whoopingcough.net to inform patients about whooping cough and to to help them diagnose it for themselves. The feedback has confirmed its value and it gets 3 thousand hits a day. The bonus for site visitors is that they can listen to the sound of the characteristic coughing on sound files and watch videos.
In 2005 I published anonymised patient data here. This enables interested people to see original material and review my conclusions independently if necessary.
Current issues are about the raised number of deaths in infants. Adults of childbearing age are now the most numerous of confirmed cases. If infants are catching it from their parents a strong case can be made for periodic boosting of pertussis immunity throughout life. This is recommended in the USA and Australia and is achieved by means of 10 yearly tetanus, low dose diphtheria and acellular pertussis vaccine.
The year by year Keyworth v England and Wales incidence table shows the number of cases in Keyworth per year, and the rate per 100,000 population. Alongside are notifications for England and Wales and the rate per 100,000 population. The ratio of the two rates is shown. This demonstrates that whooping cough in Keyworth has been been 10 and 200 times the national rate.
The same data are shown in graphical form here and is easier to appreciate than the previous table. Keyworth versus England and Wales incidence graph (both equated to cases per 100,000 population) tells the story best. Notifications have dropped off but the incidence in Keyworth has remained high and steady for 25 years, although within this pattern there are still some very interesting changes such as age incidence and periodicity. The great change is how it become and adult disease principally. There also seems to be a trend of gradual reduction in incidence over the last 10 years, inclusive of 2012.
The Average age graph shows how the average age has changed from 4 in 1977 to 34 in 2012.
The table of ages affected in each year, demonstrates how it has become a disease of adults in numerical terms.
The cases table shows the age, sex and year of infection of all cases recorded since 1977 (728), and whether there was whooping, vomiting and cyanosis/apnoea. It also gives swab status if taken, and latterly, pertussis toxin IgG positivity if tested for, and the case unique index number. There is more explanation given on the page, but it is important to understand why there are some paradoxes. There are 10 more index numbers than cases. The difference mainly represents patients who were given index numbers in too much haste and later withdrawn after deciding it was not whooping cough. The diagnosis is very largely retrospective and it is quite common to revise a clinical diagnosis at a later stage.
There is a most interesting graph that shows in incidence over the years in 4 age groups. It shows how it has become rare in the under ones, virtually gone from the 1 to 9s since pertussis was added to the preschool booster in 2001. It has reduced a little in the 10 to 14s with the preschool booster addition, but In the over 15s, the numbers have remained the same for 30 years, yet these are the ones who are apparently swelling the "increase" in official figures in 2011-12. It is more likely the result of increased adult self diagnosis (with the help of this website) and the availability of a blood test since 2006 that have put it back into family doctor consciousness.
I hope this item attracts questions and comments. If so, I would like to put the interesting ones on a separate page. I would prefer to attribute correspondents, so please state your Preferred designation or if you wish to remain anonymous. I can be emailed, or I can be contacted on +44 (0)1159830235
The original papers I have published on whooping cough are:
Outbreak of whooping cough in general practice. Jenkinson D. Br Med J 1978;277:896
Whooping cough: what proportion of cases is notified in an epidemic? Jenkinson D. Br Med J 1983;287:185-6
A search for subclinical infection during a small outbreak of whooping cough: implications for clinical diagnosis. Jenkinson D, Pepper JD. J R Coll Gen Pract 1986;36:547-8
Duration of effectiveness of pertussis vaccine: evidence from a ten year community study. Jenkinson D. Br Med J 1988;296:612-4
Natural course of 500 consecutive cases of whooping cough: a general practice population study. Jenkinson D. Br Med J 1995;310,299-302
Increase in pertussis may be due to increased recognition and diagnosis. Jenkinson D. BMJ 2012;345;e5463