Virus World

More than two-thirds of fully vaccinated people in a Texas prison caught COVID-19 during an outbreak of the Delta variant in July, but vaccines protected against severe illness, a study from the Centers for Disease Control and Prevention found. Of 185 fully vaccinated prisoners at the unnamed prison, 129, or about 70%, caught the virus, data compiled by the CDC and the Federal Bureau of Prisons showed. This was a much lower rate than the unvaccinated prisoners, 39 of 42 of whom – or about 93% — caught COVID-19 during the outbreak, said the study, published Tuesday in the CDC's Morbidity and Mortality Weekly Report. Four people, three of whom were unvaccinated, needed treatment in a hospital, the study said. One unvaccinated person died, it said.

Most of the prisoners were white men, and many had received Pfizer's vaccine at least four months before the outbreak, the data showed.  The study adds to growing evidence that COVID-19 vaccines cut the risk of severe disease and hospitalization. Prisons tend to have higher rates of COVID-19 and deaths because of cramped living conditions and underlying health conditions, the CDC said. Another CDC study from this month found that unvaccinated Americans were 11 times as likely to die of COVID-19 as vaccinated people. About 45% of people in the US are unvaccinated, according to the CDC. The latest CDC study showed that the Delta variant can spread among both vaccinated and unvaccinated people. "Infectious virus was cultured from vaccinated and unvaccinated infected persons," the study said. Measures like masks and regular testing are "critical" where physical distancing is "challenging," even if vaccination rates are high, the CDC said.

Sage says majority were likely infected shortly before or soon after jab, before immunity had time to develop.  One in 25 people hospitalised with Covid-19 since December have had at least one dose of vaccine, with the majority infected shortly before or soon after vaccination – before immunity would have had time to develop. However, few of those who developed symptoms, did so more than 2 weeks after receiving a first dose – indicating that the vaccines do help to prevent serious disease once they’ve had time to take effect. The data, presented to the government’s Scientific Advisory Group for Emergencies (Sage), could be a further indication that people are dropping their guard once they’ve received a jab, wrongly assuming that they are immediately protected. Alternative explanations include the possibility that they were infected shortly before vaccination, during the vaccine appointment itself, or that vaccination triggered symptoms in infected people who were previously asymptomatic. In minutes from its 83rd meeting on 11 March Sage said:“The observation that a significant number of people developing symptoms within a few days of a first dose may suggest some behaviour change following vaccination. It is important therefore that communications around vaccination reinforce the need for safe behaviours to be maintained.” Almost 29 million people in the UK have received at least one dose of a coronavirus vaccine so far, with some degree of immune protection thought to develop around two weeks after receiving the first jab – although a second dose is needed to achieve the highest levels of protection.

According to data submitted to Sage by the Covid-19 Clinical Information Network (CO-CIN), there were 1,802 recorded cases of vaccinated patients hospitalised with Covid-19 in the UK as of 5 March. This accounted for 4.2% (1,802/42,788) of all Covid-related hospital admissions since 8 December – the date when the first people in the UK were vaccinated. The median time between vaccination and symptom onset for these patients was five days, indicating that most of them were infected shortly before or around the time of vaccination, with the remainder infected after vaccination but before immunity had developed. “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,” the CO-CIN report said.  Data from previous vaccine rollouts, national surveys and evidence from Israel have also indicated that people may be less likely to abide by social distancing rules once they’ve been vaccinated. In its 11 March meeting, Sage emphasised the need for better government communication about how long it takes for the jab to work, and that although the Covid-19 vaccines in use in the UK are highly effective, no vaccine is 100% effective. Minutes from the meeting said: “Some people will be hospitalised with Covid-19 even after completing their full vaccination schedule. It will be particularly important to monitor the prevalence of different variants present in this group by sequencing to understand any potential immune escape. This is under way by Public Health England.” A separate document released by Sage on Friday suggested there has been a four-fold increase in confirmed cases of the Brazilian P1 variant during the fortnight of 10 March to 24 March from 5 to 21, while cases of the South African variant have increased from 190 to 305.