UK COVID-19 Update: Single Vaccine Dose Halves Transmission, Booster Jabs, Leap in Antibody Rates

Peter Russell

April 28, 2021

Editor's note, 28 April 2021: This article was updated with new information from UCL and a Downing Street briefing.

These are the UK coronavirus stories you need to know about today.

Single Vaccine Dose 'Halves Transmission'

A single dose of either the Pfizer/BioNTech or the AstraZeneca/Oxford COVID-19 vaccines reduced household transmission by up to a half, according to new research by Public Health England (PHE).

The study, published as a preprint, found that those who become infected 3 weeks after receiving a first dose of the Pfizer/BioNTech or AstraZeneca/Oxford vaccines were between 38% and 49% less likely to pass the virus on to household contacts than those who were unvaccinated.

Protection was seen from around 14 days after vaccination, with similar levels of protection across all age groups, researchers said.

PHE added that this protection was on top of the reduced risk of a vaccinated person developing symptomatic infection from SARS-CoV-2 in the first place, which was around 60% to 65% - 4 weeks after one dose of either vaccine.

The results were described as "terrific news" by Matt Hancock, England's Health Secretary.

The study involved an analysis of 365,447 households in England and more than a million contacts.

The odds ratio of becoming a secondary case was 0.62 (95% confidence interval 0.48, 0.79) in household contacts receiving AstraZeneca's ChAdOx1 nCoV-19 vaccine 21 days or more before testing positive, compared to unvaccinated cases. For household contacts of cases receiving Pfizer's BNT162b2 vaccine, the odds ratio was 0.51 (95% confidence interval 0.42, 0.62).

The researchers noted that 93% of the vaccinated cases had received just one dose of vaccine and it would be important to assess if there was any further reduction in transmissibility from receiving a second dose of vaccine when such data became available.

PHE said it was also undertaking separate studies on how vaccination affected transmission in the wider population.

Dr Mary Ramsay, head of immunisation at PHE, said: "Not only do vaccines reduce the severity of illness and prevent hundreds of deaths every day, we now see they also have an additional impact on reducing the chance of passing COVID-19 on to others."

Dr Peter English, a retired consultant in communicable disease control, told the Science Media Centre that the findings were "extremely encouraging".

He said: "They add to our reasons to hope that the vaccines will truly add to herd immunity."

Booster Jabs

The UK has ordered a further 60 million doses of the Pfizer/BioNTech vaccine to be used as part of a booster jabs programme, England's Health Secretary Matt Hancock told a Downing Street briefing.

"We have been working on a programme of booster shots...for over a year now," he said, "And we've backed some of the only clinical trials in the world looking specifically at booster shots." 

Mr Hancock also turned to the crisis in India: "The situation in India is a stark reminder that this isn’t over yet," he said.

"It shows how important it is that we are vigilant here at home."

Another Rise in SARS-CoV-2 Antibodies

An increase in the proportion of people with SARS-CoV-2 antibodies was recorded in all four UK nations, according to latest official figures.

The rise was attributed to the ongoing vaccination programme, the Office for National Statistics (ONS) said.

UK figures for the week ending April 11 showed that:

  • England: An estimated 68.3% of adults would have tested positive for antibodies – up from 54.9% 2 weeks previously

  • Northern Ireland: An estimated 62.5% would have tested positive for antibodies – up from 54.5%

  • Wales: An estimated 61.0% would have tested positive for antibodies – up from 49.1%

  • Scotland: An estimated 57.8% would have tested positive for antibodies – up from 46.0%

Sarah Crofts, senior statistician for the COVID-19 Infection Survey said: "Our data today show an increase in antibody levels across all four UK nations – reflecting the growing success of the vaccine rollout.

"In England, we estimate 7 in 10 adults would now test positive for antibodies against COVID-19. These kind of antibody levels are really encouraging as we transition out of lockdown.

The ONS analysis showed a variation in antibody positivity in regions in England, with the highest seen in the North West, at 69.9%, and the lowest in the North East, at 64.4%.

In England, the highest percentage estimate for adults testing positive was seen in people aged 70 to 74, at 87.6%.

Statisticians said a recent increase in antibody positivity in older people, following a dip in March, had probably been caused by people in these age groups receiving their second vaccine dose.

NHS App Could be Passport to the Sun

An NHS app will be used to allow people in the UK to prove whether they have had a COVID vaccine, or tested negative for the virus, before travelling abroad, a minister disclosed.

Transport Secretary Grant Shapps told Sky News: "It will be the NHS app that is used for people when they book appointments with the NHS and so on, to be able to show you've had a vaccine or that you've had testing.

"I'm working internationally with partners across the world to make sure that system can be internationally recognised."

His comments came as Spain said it hoped to open up to overseas travellers from June.

It is understood that the technology will use the NHS app for booking appointments, not the NHS COVID app that is used to check into venues.

Mr Shapps also said he would be publishing details "in the next couple of weeks" on which countries would be on the 'green list' that would exempt travellers from having to quarantine on their return to the UK.

Non-essential international travel will not be allowed until May 17 at the earliest under the Government's roadmap for lifting lockdown restrictions.

Confidence in AZ Vaccine Dented

The public's preference for the AstraZeneca/Oxford vaccine has waned since last month, with a larger proportion of people believing it could cause blood clots.

However, confidence in COVID vaccines in general was higher than it was towards the end of 2020, research led by the University of Bristol and King's College London (KCL) found.

The study showed that:

  • 17% of the public expressed a preference for the AstraZeneca/Oxford vaccine, if they had a choice of any – down from 24% towards the end of March

  • 23% of people now believe the AstraZeneca vaccine causes blood clots – up from 13% last month

  • 81% now believe that COVID vaccines are safe – compared with 73% at the end of 2020

  • 46% of people who are currently unvaccinated said they were certain to take up the offer of a vaccine, compared with 36% of the public towards the end of last year

  • 13% of the public said they were 'not at all likely' or 'definitely would not' accept the vaccine – up from 7% in July 2020

The survey also recorded a substantial change in how people from ethnic minorities viewed COVID vaccinations.

Among those from minority ethnic groups who said they might get a COVID vaccine, 45% would now prefer to be vaccinated immediately after being invited – three times the 15% who indicated they would get the vaccine as soon as it became available last year, before the rollout had begun.

The findings were based on a sample of 4896 adults aged 18 to 75 carried out by Ipsos between April 1 and 16.

Prof Bobby Duffy, director of the Policy Institute at KCL, said: "The blood clot scare has affected how some of the public view the Astra Zeneca vaccine – but has not reduced confidence in vaccines overall. In fact, the trend has been towards increased commitment to get vaccinated – and quickly – as the rollout has progressed so well, with no sign of serious widespread problems. People have had more time and real-world experience to help them make up their minds.

"However, this also means that the naturally sceptical have also affirmed their views, with a near doubling since July last year – from 7% to 13% – of those who say they are not at all likely to or definitely won’t get vaccinated. This shows there is still no room for complacency in clearly communicating the vital benefits of vaccination, given the need to cover a very large proportion of the population in order to truly contain the virus."

A Third COVID-19 Wave 'Not Inevitable'

A third COVID-19 wave across the UK is not inevitable, according to a paper from the Tony Blair Institute for Global Change.

The paper said that based on modelling by SAGE scientists, the Government's current roadmap strategy to exit lockdown restrictions on June 21 risked a jump in infections that could result in between 20,000 and 40,000 further deaths and upwards of 100,00 further hospital admissions.

The paper warned that the planned lifting of restrictions "is at risk of running too far ahead of the vaccination rollout", and that "protection afforded by inoculation and past infections looks set to fall short of what will be needed to reach herd immunity even once the vaccine has been offered to all adults".

However, the continuing vaccination programme, coupled with a summer surge in COVID-19 cases, could lead to a substantial "overshoot" of the herd immunity threshold, it suggested.

The paper made a number of recommendations, including delaying the end to COVID lockdown restrictions by a month, and extending the vaccination programme to adolescents.

Headache Tops List of Vaccine Side-effects

Headache, fatigue, and tenderness were the most reported side-effects of the Pfizer/BioNTech and AstraZeneca/Oxford COVID-19 vaccines, a study found.

The analysis by researchers from King's College London (KCL), using data from 627,383 users of the ZOE COVID Symptom Study app, found fewer side effects in the general population than reported in trials of both vaccines.

Results, published in The Lancet Infectious Diseases,  showed that:

  • 25.4% of vaccinated people indicated experiencing one or more systemic side effects

  • 66.2% reported one or more local side effects

  • 13.5% of participants reported side-effects after their first Pfizer dose

  • 33.7% reported side-effects after the first AstraZeneca dose

  • The most reported systemic side effect was headache – 7.8% after the first Pfizer dose, and 22.8% after the first AstraZeneca dose

  • 21.1% of people reported fatigue after a first dose of AstraZeneca, and 8.4% after a first dose of Pfizer

  • 22.0% said they had side-effects after the second Pfizer dose

Tim Spector, lead scientist on the ZOE COVID Symptom Study app, and professor of genetic epidemiology at KCL, said: "The data should reassure many people that in the real world, after-effects of the vaccine are usually mild and short-lived, especially in the over 50s who are most at risk of the infection."

The study also found a significant decrease of infection risk starting from 12 days after the first dose of a vaccine compared to a control group.

The reduction reached at least 21 days after the first dose was 60% for the AstraZeneca vaccine, and 69% for the Pfizer vaccine.


Need for New Post-pandemic Approach to Public Health

COVID-19 has highlighted the need for a multidisciplinary approach to improving public health, experts said.

Speaking at the external launch of University College London's Health of the Public, Prof Chris Whitty, England's chief medical officer, said: "The pandemic has demonstrated how different elements of the health of the public interact."

The virtual school, which began work last September, aims to harness the efforts of local communities, governments, the NHS, and local authorities to address the most pressing public healthcare challenges.

It was established to take forward ideas presented in the Academy of Medical Sciences report, 'Improving the Health of the Public by 2040'.

Dame Anne Johnson, the school's co-director, said: "To ensure our society has more resilient public health in the future, we will need to bring together many different disciplines including engineering, environmental science, law, social science, and others along with traditional population and medical sciences."

Prof Whitty added that the approach was needed because "COVID-19 has been particularly problematic in areas of deprivation in the UK, in some ethnic minority groups, and in people with pre-existing non-infectious problems".

See more global coronavirus updates in Medscape’s Coronavirus Resource Centre.


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