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AstraZeneca, Pfizer COVID-19 Vaccine Antibodies Start Declining After 10 Weeks, Lancet Study Reveals

AstraZeneca, Pfizer COVID-19 Vaccine Antibodies Start Declining After 10 Weeks, Lancet Study Reveals
Antibodies From Pfizer, AstraZeneca’s COVID-19 Vaccine Fades After 10 Weeks, Lancet Study Reveals

Got jabbed with the COVID-19 vaccines? A new study by Lancet has revealed that the antibodies start declining after 10 weeks. Read on to know more.

Written by Satata Karmakar |Updated : July 28, 2021 4:26 PM IST

How long are you immune after receiving both the shots of the COVID-19 vaccine? Can you go out without wearing a mask and still not get infected? questions regarding antibody levels post-vaccination have been circulating for a long time now. However, a recent study published in The Lancet Journal has revealed that the total antibody levels start to wane six weeks after complete immunization with Pfizer and AstraZeneca vaccines, and can reduce by more than 50 per cent over 10 weeks. According to the researchers, if the antibody levels carry on dropping at this rate, there are concerns that the protective effects of the vaccines may also begin to wear off, particularly against new variants. However, they said, how soon that might happen cannot be predicted yet.

Pfizer's COVID-19 Vaccine Vs AstraZeneca

The study also found that antibody levels are substantially higher following two doses of the Pfizer vaccine than after two shots of the AstraZeneca preventive, known as Covishield in India. The researchers stated that the antibody levels were also much higher in vaccinated people than those with prior SARS-CoV-2 infection. "The levels of antibody following both doses of either the AstraZeneca or Pfizer vaccine were initially very high, which is likely to be an important part of why they are so protective against severe COVID-19," one of the researchers was quoted as saying. She further added, "However, we found these levels dropped substantially over the course of two to three months."

Should You Still Take The Vaccine Shots?

Yes, researchers have stated that one should still get jabbed with the COVID-19 vaccines. Wondering why? Let's dig in a little more into the study. The findings based on data from over 600 people aged 18 and above were consistent across all groups of people regardless of age, chronic illnesses, or sex, according to the researchers. The authors highlight that although the clinical implications of waning antibody levels are not yet clear, some decline was expected and current research shows that vaccines remain effective against severe disease.

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For Pfizer, antibody levels reduced from a median of 7506 Units per millilitre (U/mL) at 21 41 days, to 3320 U/mL at 70 or more days. For the AstraZeneca vaccine, antibody levels reduced from a median of 1201 U/mL at 0 20 days to 190 U/mL at 70 or more days, over a five-fold reduction.

"When we are thinking about who should be prioritised for booster doses our data suggests that those vaccinated earliest, particularly with the AstraZeneca vaccine, are likely to now have the lowest antibody levels," said Professor Rob Aldridge from UCL Institute of Health Informatics.

Booster Doses For Adults And Those With Underlying Health Complications

The findings support recommendations that adults who are clinically vulnerable, those aged 70 years or over, and all residents of care homes for older adults should be prioritised for booster doses, the researchers said. In addition, those who were vaccinated with the AstraZeneca vaccine are likely to have much lower antibody levels than those vaccinated with the Pfizer vaccine, they noted.

"This may also need to be considered when deciding who should be prioritised when boosters are rolled out," Aldridge said in the statement. The team acknowledged certain limitations in the data, including a small sample size for some groups.

The researchers noted that each individual only contributed one sample, so they cannot yet confirm how quickly antibody levels drop for each individual, or whether these would continue to drop or reach a stable level over the next few months. They also noted that different people will have different levels of immunity depending on the virus neutralising ability of their antibodies as well as their T-cell responses.

"Even when measurable antibody levels are low, there is likely to be continuing immune memory that could offer long-term protection," the authors of the study noted. They said further research will be important to establish if there is an antibody level threshold needed for protection against severe disease.

(With inputs from Agencies)