Single jab 'cuts transmission by up to half' - and common side effects revealed
- Credit: Danielle Booden
A single dose of a Covid-19 vaccine can cut transmission of coronavirus by up to half, a new study has found.
The breakthrough findings offer further hope that the pandemic can be brought under control as vaccinated people are far less likely to pass the virus onto others.
The Public Health England study found people given a single dose of either the Pfizer/BioNTech or Oxford/AstraZeneca vaccines - and who became infected at least three weeks later - were between 38pc and 49pc less likely to pass the virus on to people living in their homes, compared to those who were unvaccinated.
Protection was seen from around 14 days after vaccination, with similar levels regardless of a person's age.
Other studies have already shown that both vaccines are highly effective at stopping people getting sick and ending up in hospital.
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Experts will now assess whether two doses of vaccine can cut transmission of the virus even further, and more work is being carried out on transmission in the general population.
PHE said similar results could be expected in places where the risk of transmission is similar to the home, such as shared accommodation and prisons.
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The study included data from January and February, when the Kent strain was dominant in the UK.
Health secretary Matt Hancock said: "This is terrific news - we already know vaccines save lives and this study is the most comprehensive real-world data showing they also cut transmission of this deadly virus.
"It further reinforces that vaccines are the best way out of this pandemic as they protect you and they may prevent you from unknowingly infecting someone in your household.
"I urge everybody to get their vaccines as soon as they are eligible and make sure you get your second dose for the strongest possible protection."
The study, yet to be peer-reviewed, included over 57,000 people living in 24,000 households who were the contacts of a vaccinated person.
They were compared with nearly one million contacts of people who had not had a vaccine.
Contacts were defined as secondary cases of coronavirus if they tested positive two to 14 days after the initial household case.
Most of the people in the study were under the age of 60.
Dr Mary Ramsay, head of immunisation at PHE, said: "Vaccines are vital in helping us return to a normal way of life.
"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.
"I encourage anyone who is offered a vaccine to take it as soon as possible.
"While these findings are very encouraging, even if you have been vaccinated, it is really important that you continue to act like you have the virus, practise good hand hygiene and follow social distancing guidance."
The Pfizer and AstraZeneca vaccines are credited with having saved 10,400 lives among the over-60s as of the end of March.
Data out last week from the national Covid-19 Infection Survey run by the University of Oxford and the Office for National Statistics (ONS) also found that vaccines are likely to cut transmission.
Great Yarmouth will tomorrow (Thursday) become the latest place in Norfolk and Waveney where a large mass vaccine centre will open.
The centre at Market Gates shopping centre will follow those in Norwich, Attleborough, King's Lynn, North Walsham, Harleston, Lowestoft and Downham Market.
Most common side effects revealed
Meanwhile, separate research has shown one in four people experience mild, short-lived systemic side-effects after receiving either the Pfizer or AstraZeneca coronavirus vaccine.
Headache, fatigue and tenderness are the most common symptoms, with most effects peaking within 24 hours after vaccination, usually lasting one to two days, according to the study.
The paper, published in the Lancet Infectious Diseases, compared both jabs and investigated the prevalence of mild side-effects of the UK's vaccination programme.
The analysis by researchers from King's College London of data from the Zoe Covid Symptom Study app found fewer side-effects in the general population with both the Pfizer and AstraZeneca vaccines than reported in trials.
Tim Spector, professor of genetic epidemiology at King's College London and lead scientist on the Zoe Covid Symptom Study app, 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.
"Rates of new disease are at a new low in the UK, according to the Zoe app, due to a combination of social measures and vaccination, and we need to continue this successful strategy to cover the remaining population."
The analysis looked at the differences of reported side-effects from the first two vaccines to be offered in the UK.
Systemic effects - meaning side-effects excluding the injection site - included headache, fatigue, chills and shiver, diarrhoea, fever, arthralgia (joint pain), myalgia (muscle pain), and nausea.
Local side-effects - where the injection took place in the arm - included pain, swelling, tenderness, redness, itch, warmth and swollen armpit glands.
The data comes from 627,383 users of the Zoe Covid Symptom Study app who self-reported systemic and local effects within eight days of receiving one or two doses of the Pfizer vaccine or one dose of the AstraZeneca vaccine between December 8 and March 10.
Overall, the study found that 25.4pc of vaccinated people indicated suffering from one or more systemic side-effects, whereas 66.2pc reported one or more local side-effects.
Around 13.5pc of participants reported side-effects after their first Pfizer dose, 22pc after the second Pfizer dose and 33.7pc after the first AstraZeneca dose.
The most reported systemic side-effect was headache, with 7.8pc of people reported suffering from headaches after the first Pfizer dose and 13.2pc after the second Pfizer dose.
The research found more side-effects in those under the age of 55, and among women.
Participants who had previously had coronavirus were three times more likely to have side-effects affecting the whole body after receiving doses of the Pfizer vaccine than those without known infection.
They were almost twice as likely after the first dose of the AstraZeneca vaccine.