Covid vaccine: One in 14 hospital patients with disease had had first dose

The data emerged in the latest publication from the Isaric (International Severe Acute Respiratory and Emerging Infection Consortium) study, which is tracking Covid hospitalisations among vaccinated and unvaccinated patients in Scotland, England, and Wales.

Of the 52,280 patients enrolled in the study since December 8 - when Covid vaccines were first administered in the UK - 3,852 were vaccinated people hospitalised with the disease by March 10.

Vaccinated patients (in turquoise) accounted for a tiny fraction of the total patients hospitalised with Covid from December 8. Graphics show second wave starting from September 1

Researchers were able to identify a confirmed PCR positive case in addition to details of the dates of vaccination and onset of symptoms for 1,818 of these patients.

They found that the vast majority - 1,292 - had become ill within the first 21 days of their first dose, suggesting that they were infected "shortly before or around the time of vaccination" or "before immunity had developed".

Nearly 700 were people aged over 75, including elderly care home residents.

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The researchers said it was possible that elderly and vulnerable people who had been shielding "may have inadvertently been exposed and infected either through the end-to-end process of vaccination, or shortly after vaccination through behavioural changes where they wrongly assume they are immune".

However, 526 of the 1,818 patients (29%) had developed Covid symptoms more than 21 days after their first vaccination, when antibody protection against the virus should have peaked.

Of these individuals, 113 had died by the time the current phase of the study ended on April 10. Most - 97 - were in the 75-plus age group.

The report, which is one of the first in the world to investigate 'vaccine failure' rates in-depth, is being shared today with the UK Government's Sage expert group (Scientific Advisory Group on Emergencies).

There was a steady and steep decline in symptomatic infections in the weeks after a first dose. Researchers followed up outcomes for the 1818 patients (in turquoise) who had a confirmed positive PCR test

Professor Calum Semple, co-author on the study and a expert in viral disease outbreaks at Liverpool University, said: "This analysis was designed to give Sage a very early signal that the vaccine was working in the real world.

"But it also shows that the vaccine isn't perfect. The absolute numbers of people being admitted to hospital after 21 days from their first dose is tiny, but it does occur.

"It's mostly occurring in the group most at risk of severe disease anyway...these people are very frail, very old, elderly.

"We're not saying the the vaccine doesn't work - we're saying that the vaccine does work. This is good real-world evidence of it working.

"But there are a few failures, and when these failures do occur sadly people die but that's because they're elderly and frail."

The authors caution that the data available at this stage does not give any insight into how protection changes after a second vaccine dose, or the duration of immunity.

Table providing a breakdown for the 1818 hospitalised vaccinated patients, with a positive test, by date of symptom onset

They add that it does not cover all hospitalised patients - only those enrolled in Isaric, and a subset for whom a positive test, date of vaccination, and date of symptom onset were available.

They also stress that the demographics of vaccinated patients are necessarily skewed towards older and frailer adults due to the mainly age-based focus of the rollout, and because the study does not include vaccinated people in the community who never became sick enough to require hospitalisation. 

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Yet at the same time they note that the study period also coincided with strict national lockdowns which were pushing down the epidemic curve and reducing the risk of virus exposure in the community as the rollout moved down the priority groups.

For this reason Prof Semple, who is originally from Edinburgh and sits on both Sage and Nervtag (the New and Emerging Respiratory Virus Threats Advisory Group which advises the Department of Health), said the figures should not be used to extrapolate that the Covid vaccines are 99% effective at preventing death three weeks after a single dose.

"We know that can't be true," he said, but stressed that the results were "very reassuring".

"When we looked at that decay curve in March, it was a moment of joy. It does show the vaccine working in this high risk group."

Prof Semple said seeing the decay curve was 'a moment of joy' that the vaccines are working. Graph A shows all hospitalised vaccinated patients with symptoms, and B shows those with confirmed Covid from a positive PCR test

Prof Semple said the findings - particularly around the 113 deaths - should also serve as a reminder to people to remain cautious even after vaccination.

He said: "A great many people are acquiring Covid within two weeks of being vaccinated, which does indicate that people are letting their guard down.

"There is evidence here than people are unfortunately assuming they are fully protected very quickly after vaccination and that's not the case.

"[The 113 deaths] will surprise people, and the trouble is it will be amplified on social media to say that the vaccines are no good because 'look what happened to my Granny'.

"But what they're not seeing is the 999 other Grannies out of a 1000 who consequently didn't die."

Professor Calum Semple

Dr Annmarie Docherty, co-author and honorary consultant in critical care medicine at Edinburgh University, added that the findings are partly complicated because many of those vaccinated more recently have been at much lower risk of infection compared to those vaccinated in January and February when virus prevalence was much higher.

She said: "While [these results are] good news, potentially we're under-representing vaccine failure because people aren't being exposed to the virus.

"I think this probably emphasises the importance of ongoing vaccination of lower risk groups.

"If there is a surge and there is more coronavirus around, the vaccine isn't 100% effective so it is possible that elderly people will catch coronavirus and, despite being vaccinated, will end up in hospital and may die.

"It provides strong support for widespread vaccination."

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Prof Semple added: "In my mind, we still have a substantial number of younger people who are not vaccinated. They are the most socially mobile, and consequently will be the greatest amplifiers of disease.

"We now have evidence of some vaccine failure in high risk populations, so while it is a good news story there are substantial gains to be had by pressing forward with the vaccination programme and sticking to the cautious lockdown."

Cases in Scotland are at levels last seen in mid-September (daily positive plus seven-day rolling average, in orange) Source: Scottish Government

To date, almost 62% of adults in Scotland have had a first vaccine dose, and 26% have had both doses.

There are currently 70 people in hospital with a recent Covid diagnosis, down 97% from a peak of 2,053 in January.

In the past seven days, 1,453 people have tested positive in Scotland - the first time since mid-September that the weekly count has dipped below 1500.

From May 17, in both Scotland and England, hospitality venues will able to open indoors and serve alcohol to groups of up to six people.

International travel could also resume, subject to certain restrictions.

England's roadmap forecasts an end to social distancing from June 21, with nightclubs and large events allowed to resume.

The Scottish Government has said it hopes to move into Level Zero by the end of June, when people will be able to socialise indoors in groups of up to four households.