The Covid-19 pandemic has confounded medical experts and policy makers alike since it began in 2020. More than a year on, they are grappling with an emerging new mystery involving “breakthrough cases” — people who caught Covid-19 despite being vaccinated.
This repo contains a dataset and notebook analysing 271 such breakthrough Covid-19 cases in Singapore, via publicly released data from the Ministry of Health’s website.
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Of the 271 breakthrough cases, 196 (72.3%) involve full vaccinated individuals who have had two shots of the Moderna or Pfizer-BioNTech vaccines, while 75 (27.7%) had only one shot.
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There are only 20 mentions of the Delta or B1617 variant in the case notes, representing just 7.4% of the 271 breakthrough cases. But it is unclear if absence of evidence is evidence of absence in this instance.
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About a third, or 92 of the 271 breakthrough cases, were asymptomatic, while the rest experienced a range of symptoms from fever to runny nose to fatigue.
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For breakthrough cases who were fully vaccinated, the median number of days between their second shot and confirmation of Covid-19 infection is 59 days. For breakthrough cases who only got one shot, the median number of days between their one and only jab and confirmation of Covid-19 infection is just 13 days.
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Men make up 62% of the breakthrough cases, while 149, or 55% of the 271 cases, are aged 50 and above. The median age of the breakthrough cases is 52. Singapore started its vaccination programme by focusing first on older segments of the population as well as frontline workers. The socio-demographic profile of breakthrough cases could well change in the coming months as younger people are vaccinated in larger numbers. As such, I would avoid jumping to conclusions based on demographic trends at this point, though they are well worth a look.
This is not a medical study, and I'm not a virologist or vaccine expert.
More details in this Medium post.