ECONOMYNEXT – Researchers in Sri Lanka have found that antibody levels created by the first dose of the AstraZeneca COVID-19 vaccine drops in elderly people within 16 weeks if the second dose is not taken within that period.
The finding raises concerns about adequate immunity in the elderly among 575,000 Sri Lankans who, after months of waiting, will finally get their second shot of AstraZeneca starting Sunday (02).
A paper written by a team led by Prof Neelika Malavige, who heads the Department of Immunology and Molecular Medicine at the University of Sri Jayawardanapura, was published in globally reputed Nature Communications, an online science journal published by Nature Research, a division of international publisher of science magazines Springer Nature.
“What we have looked at are the antibody responses following a single dose of the vaccine,” Malavige told EconomyNext via e-mail.
“What we have found is that, while in younger people antibodies are maintained at a reasonable level even at 16 weeks, it reduces in the elderly. Therefore, it is important to give the second dose at 12 weeks or may be earlier in the elderly. Protection offered by a single dose may wane with time, especially for variants like delta,” she said.
The study was conducted among 655 healthcare workers who got their first dose of AstraZeneca in February and March.
“Basically, in this study, we found that after a single dose of the Covishield (AstraZeneca) vaccine, 93.4% individuals developed antibodies and 97.1% developed neutralizing antibodies (the protective type of antibodies),” Malavige said.
“Antibodies to delta was not measured, as delta was not a problem during the time the study was conducted (in February and March),” she said.
Over 400,000 Sri Lankans received their first AstraZeneca dose in February and more than 450,000 got in March, health ministry data showed. Most of them were over 60 years of age as the government initially focused on the elderly. Some 575,000 who have received first AstraZeneca dose are awaiting their second jab.
Originally, the second dose was scheduled to be administered in 11 weeks, COVID-19 vaccination cards carried by recipients of the first dose showed.
The long delay was due to the government’s failure to secure vaccine consignments after an initial plan to buy 10 million Covishiled doses from India did not pan out in the wake of a devestating second wave across the Palk Strait. A fire at the vaccine manufacturing plant of Serum Institute of India also may have contributed. Many Asian and African countries faced the same scarcity.
Sri Lanka health authorities said it had yet to receive an official copy of the research study yet to decide if it should consider a fresh vaccine rollout for the elderly who were administered AstraZeneca five months ago.
“Even if we get the report, we will have to review it with another medical team and only then we will proceed to take necessary decisions,” Health Services Deputy Director Dr Hemantha Herath told EconomyNext.
Oxford University report
A study conducted by the Oxford University, published on June 28, says “a long interval between first and second AstraZeneca doses does not compromise the immune response”.
In fact, a late second dose in people aged 18-55, and a third dose continue to boost antibodies against coronavirus, the UK-based study found.
“There is an excellent response to a second dose, even after a 10-month delay from the first,” Andrew Pollard, Professor of Pediatric Infection and Immunity and Lead Investigator of the Oxford University trial of the vaccine, said in the Oxford University report.
According to the Oxford report, antibody levels had increased in its study participants after a 45-week delay between the first and second dose.
It suggests that “a longer delay between first and second doses may be beneficial, resulting in an increased antibody titer and enhanced immune response after the second dose.”
Explaining the Oxford Research, Prof Malavagie said: “Delaying the second dose between 15 to 25 weeks resulted in a significantly higher antibody response than when the second shot was given between 8 to 12 weeks. Therefore, it looks [like] it’s better to delay the second shot to 15 to 25 weeks.”
With the delta variant of Indian origin starting to spread in Sri Lanka, health officials have warned of a fourth wave.
The US Center for Disease Control and Prevention (CDC) has described the delta variant of the coronavirus as being as transmissible as chickenpox and cautioned it could cause severe disease, the Washington Post said, citing an internal CDC document.
COVID-19 infections have increased by 80% over the past four weeks in most regions of the world, WHO director-general Tedros Adhanom Ghebreyesus said on Friday (30). Deaths in Africa – where only 1.5% of the population is vaccinated – rose by 80% over the same period.
“The issue is [that] the efficacy (not immunogenicity) of the vaccine, with a single dose, for delta is 30 percent only. Which means 70 percent will develop symptomatic disease with delta (some severe illness and death) with just one dose,” Malavagie said.
“Therefore, given a situation where you have delta, although antibody levels are higher when you delay the second dose to 15 to 25 weeks (five to six months), the majority of vaccine recipients are not protected against delta during this time. This is why in the UK, they have brought forward the second dose to eight weeks, with delta taking off.” (Colombo/Jul31/2021)