LONDON: The total level of antibodies began to decrease six weeks after immunization complete with Pfizer and AstraZeneca vaccines, and can reduce more than 50 percent more than 10 weeks, according to a study published in the Lancet journal.
Researchers from the University College London (UCL) in the UK noted that if the antibody level continues to decline at this level, there is concern that the effects of protection from vaccines can also start tiring, especially against new variants.
However, they said, how fast it might happen unpredictable.
The Virus Virus Watch study also found that the antibody level was substantially higher after two doses of the Pfizer vaccine than after two AstraZeneca prevention shots, known as Covishield in India.
The antibody level is also much higher in people who are vaccinated than those who suffer from SARS-COV-2 infection before, they said.
“The antibody level follows both doses either astrazeneca or the initial Pfizer vaccine is very high, which is likely an important part of why they are so protective against severe Covid-19,” said Madhumita Shrotri from the UCL Health Informatics Institute.
“However, we found this level down substantially for two to three months,” Shrotri said in a statement.
Findings based on data from more than 600 people aged 18 years and over are consistent in all groups of people regardless of age, chronic diseases, or sex, according to researchers.
The authors highlighted that even though the clinical implications of the antibody level reduced unclear, some declines are expected and the current research shows that the vaccine remains effective against severe diseases.
For Pfizer, the antibody level is reduced from the median 7506 units per milliliter (U / mL) at 21-41 days, up to 3320 U / mL at 70 days or more.
For AstraZeneca vaccines, the antibody level decreases from the median 1201 U / mL at 0-20 days to 190 U / mL at 70 days or more, more than a fivefold reduction.
“When we think about who should be prioritized for a booster dose.
Our data shows that they are the earliest vaccinated, especially with the AstraZeneca vaccine, the possibility of now has the lowest antibody level,” said Professor Rob Aldridge from Informatics Informatics UCL.
These findings support recommendations clinically vulnerable adults, those aged 70 years or more, and all residents of home care for older adults must be prioritized for a booster dose, the researchers said.
In addition, those who are vaccinated with Astrazeneca vaccines tend to have a much lower level of antibodies than vaccinated with the Pfizer vaccine, which they recorded.
“It might also be considered when deciding who should be prioritized when the booster was launched,” Aldridge said in the statement.
The team recognizes certain limitations in the data, including small sample size for several groups.
The researchers noted that each individual only contributed one sample, so they could not confirm how quickly the antibody level dropped for each individual, or whether this would continue to fall or reach a stable level over the next few months.
They also note that different people will have different immune levels depending on the ability to neutralize their antibody viruses and their cell-t responses.
“Even when a measurable level of antibodies, there is a possibility that it will continue the immune memory that can offer long-term protection,” said the author of this study.
They said further research would be important to be established if there was an antibody level threshold needed for severe disease.