LONDON: Fully vaccinated people can contract and continue the Delta variant from SARS-COV-2, the virus which causes Covid-19, in household settings, but with a lower level than people who are not vaccinated, according to a study published in the journal Lancet infection disease.
Researchers led by Imperial College London, England, found that people who were vaccinated cleaning infections faster, but the burden of the peak viral among them similar to those that were seen in individuals who were not vaccinated, which could explain why they can easily continue Virus at home.
The researchers noted that most Covid-19 transmissions were known to occur in households but there was limited data on the risk of transmission of Delta variants from people who were vaccinated with asymptomatic or mild infections in the community.
“Vaccines are very important for controlling pandemics, as we know they are very effective in preventing serious diseases and deaths from Covid-19,” said Professor Ajit Lalvani from London Imperial College, who tore learning.
“However, our findings show that vaccinations are not enough to prevent people from being infected with Delta variants and spread them in household settings,” Lalvani added.
The researchers noted that transmission between vaccinated people made it important for people who were not eliminated to protect themselves from obtaining infection and severe Covid-19, especially because more people would spend time in the near future during the winter months .
The study enrolled 621 participants, identified by the British Contact Search System, between September 2020 and September 2021.
All participants have a small Covid-19 disease or not show symptoms.
They have a daily PCR test to detect infection, regardless of whether they have symptoms or not.
The researchers conducted PCR tests on the swab sample provided every day by each participant for 14-20 days.
Changes from time to time in viral load – the number of viruses in someone’s nose and throat – is estimated by modeling PCR data.
A total of 205 household contacts the Delta variant index case was identified, including 53 positively tested for Covid-19.
Among the contact who was vaccinated with the Delta variant, the length of the average time since vaccination was 101 days, compared to 64 days for non-infected contacts, the researchers said.
This shows that the risk of infection increases within three months after receiving the second dose of vaccine, the possibility of reduced protective immunity, they said.
The authors refer to the vaccine reduced as an important evidence for all those who are eligible to receive booster shots.
A total of 133 participants had their daily viral load trajectory analyzed, including 49 had a pre-alpha variant and was not vaccinated, 39 had alpha and was not vaccinated, 29 had a delta and was fully vaccinated, and 16 had deltas and was not vaccinated.
The study found that viral load declined faster among people who were vaccinated infected with Delta variants compared to people who were not vaccinated with Delta, Alpha, or Pre-Alpha.
However, the author notes that vaccinated people do not record lower peak viral loads than people who are not vaccinated, which can explain why the Delta variant can still spread despite vaccination because the most contagious people during the peak viral load phase.
“Understanding the extent to which vaccinated people can continue the Delta variant to others is the public health priority,” said Anika Sitahayagam, the author of co-lead from this study.
“By making repetitive sampling and often from Covid-19 case contacts, we find that vaccinated people can contract and forward infection in the household, including for vaccinated household members,” Santayagam said.
These findings show that the continuation of public health and social steps to curb transmissions – such as masks wear, distance social, and testing – still important, even in vaccinated individuals.
The authors recognize some limitations for their studies.
Because of the nature of community testing based on British symptoms, only contacts from the case of the recruited symptomatic index, the researchers said.
As this study was carried out when the infection circulated widely, it could not be excluded that other household members might have been infected and transmit Covid-19 to the index case, he added.