Fully vaccinated people almost twice as likely to have no symptoms as unvaccinated people if they catch COVID-19, study finds

• Fully vaccinated people who caught COVID-19 were twice as likely to have no symptoms, study found.

• But most of the people vaccinated in the study did not catch COVID-19.

• The study authors said that vaccinated people who have interacted with vulnerable people should be tested regularly.

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Fully vaccinated people who catch COVID-19 are almost twice as likely to have no symptoms as those who haven’t had a vaccine, suggests a large UK study.

The study by researchers at King’s College London was published Wednesday evening in the medical journal The Lancet Infectious Diseases. It found that less than 0.2% of the 971,504 fully vaccinated adults studied caught COVID-19 at least a week after their second dose.

But, for the 2,370 people who were infected after vaccination, the odds of having no symptoms increased by 94% compared to an unvaccinated person, the study authors said.

Scientists also found that the likelihood of catching COVID-19 with five or more symptoms in the first week of illness was reduced by about a third in people who were fully vaccinated. The likelihood of being hospitalized with COVID-19 after two doses of a COVID-19 vaccine has been reduced by two-thirds, they said.

The study authors said the results underscored the importance of testing vaccinated people regularly, regardless of symptoms. This was especially the case if they interacted with unvaccinated people or people vulnerable to COVID-19, such as older people or those with underlying health conditions.

Dr Claire Steves, co-lead author of the study, said in a statement that the findings “underscore the crucial role vaccines play in broader efforts to prevent COVID-19 infections, which should always include d other personal protective measures such as wearing a mask, frequent testing and social distancing. “

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The research, which was funded by the UK government, used the Zoe app, a symptom tracker with more than 4.7 million users worldwide.

The researchers compared those who said they had been vaccinated with the vaccines from Pfizer, Moderna or AstraZeneca and those who were not vaccinated. They took into account other factors such as age, health risk factors and location that may affect the results.

Symptoms they looked at included: fever, chills, persistent cough, fatigue, shortness of breath, loss of smell, hoarse voice, chest pain, stomach pain, diarrhea, confusion, eye discomfort, dizziness, sore throat, muscle pain unusual, blisters on the feet, worse hay fever, hair loss and brain fog.

The self-reported nature of the data means that some data was inaccurate or missing. COVID-19 infection has been proven either by a lab test or a faster lateral flow test.

Variant protection

The study, which took place between December 8, 2020 and July 4, captured infections caused by both the once-dominant Alpha variant and the highly infectious Delta variant, which has mutations that help it avoid immune response. But the variant that participants caught was not examined in the study.

Previous real-world studies have shown that Pfizer’s and AstraZeneca’s vaccines are 88% and 60% effective against COVID-19, respectively, with symptoms caused by the Delta variant which is now the most common in most areas. countries of the world including UK and US.

Dr Sara Oliver, head of epidemic intelligence at the CDC, said in a presentation Monday that since the onset of Delta, the vaccine’s effectiveness against hospitalization has ranged from 75% to 95%.

In the United States, 52.4% of people are fully vaccinated, while in the United Kingdom, 64% of Britons are fully vaccinated, according to Johns Hopkins University.

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