…as WHO group says delaying the second dose may increase protection

By Vishani Ragobeer

MINISTER of Health Dr. Frank Anthony has highlighted that Guyana will be delaying the time between the first and second doses of the Oxford-AstraZeneca vaccine for COVID-19, citing new reports from the World Health Organisation (WHO) which indicate that this will increase the protection offered.

“The Scientific Committee of the WHO is actually recommending that you should get that second dose between the eighth to 12th week and the efficacy would be higher,” Dr. Anthony said during his daily COVID-19 update with the Department of Public Information (DPI) on Monday.

Guyana began the rollout of COVID-19 vaccines last Thursday, administering the first of two doses to frontline health workers at the Georgetown Public Hospital Corporation (GPHC) and at the National Infectious Diseases Hospital, at Liliendaal, Greater Georgetown. Some 668 health workers were vaccinated on Thursday and Friday.

Initially, health workers were expected to receive the second dose of the vaccine — known as the ‘booster’ dose — about three weeks after the initial vaccination, but the Health Minister noted that a decision was made to increase that to between eight to 12 weeks. This, according to studies he referenced, has shown to increase the efficacy of the vaccines.

Last Wednesday, the WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) suggested this eight to 12-week interval between the two doses of the COVID-19 vaccine.

This Oxford-AstraZeneca vaccine, which is manufactured in India by the Serum Institute, has an efficacy of 62 per cent, while it offers 100 per cent protection against the severe form of COVID-19, hospitalisation and death in a primary analysis of Phase III clinical trials. However, studies carried out in a smaller subgroup reported that the vaccine is 90 per cent efficacious, with a lower dose than the required two doses.

Now, according to a newer study from the Oxford University that is under review at the Lancet, a single standard dose of the vaccine provided 76 per cent protection (or efficacy) overall against symptomatic COVID-19 in the first 90 days (about three months).

Then, vaccine efficacy reached 82.4 per cent after a second dose in those persons with a dosing interval of about 12 weeks. As reported by Reuters, Chief Investigator of the Oxford Vaccine Trial, Andrew Pollard, said the data showed the 12-week interval between doses was “the optimal approach to rollout, and reassures us that people are protected from 22 days after a single dose.”

On Monday as well, Immunologist and Chairman of the University of the West Indies (UWI) COVID-19 Task Force, Professor Clive Landis related that the AstraZeneca vaccine has shown 76 per cent efficacy after one shot and 82 per cent efficacy after the booster shot in the latest phase three clinical trial involving more than 35,000 people in the UK, South Africa and Brazil.

In a release from the UWI, Professor Landis highlighted that the rollout of the Oxford-AstraZeneca vaccine in several Caribbean countries “marks the start of a new phase in the pandemic in which we start the ‘fight back’ against COVID-19.”

Additionally, the release highlighted that this vaccine has been administered to over 10 million people in the UK without serious side effects, and has an excellent safety profile.

“This is an exciting time in the pandemic in which we have the opportunity to save lives and curb the spread. I really want to urge all persons who are eligible according to their risk category by age or profession to take the vaccine,” Professor Landis said.

NO ADVERSE REACTIONS

Dr Anthony also highlighted that there have been no adverse reactions recorded so far, from the pool of local workers vaccinated. There are usually two types of side effects from vaccines, generally. The first types are those common side effects such as soreness at the vaccination site, headaches, mild fevers and fatigue.

“It shows that your body is reacting to the vaccine, which means that your immune system is working and starting to produce the antibodies to fight off COVID-19,” Dr. Anthony said.

The second type, he explained however, are those adverse events which are quite rare. These adverse reactions are usually anaphylactic shocks, which mean that an individual develops an allergy to the vaccine.

“If the person develops this, generally it would develop within 15 to 20 minutes, which is why when we finish administering the vaccine, we keep the person who has received the vaccine for 15 to 20 minutes for medical observation and once everything is okay we let them go,” Dr. Anthony highlighted.

Now that Guyana has begun vaccination, the aim is to ensure that the country can get to a point of herd immunity. Herd immunity will occur once about 80 per cent of the population is immune to the disease, and vaccination is a way of ensuring immunisation.