COVID-19 vaccine mix and match, booster dose in UAE, ideal gap - 10 key questions answered

Dubai: As the UAE’s vaccination roll-out reaches new targets, a few questions are still on the minds of some residents. We look at the 10 most frequently asked questions. Besides top officials who have answered such queries in the public domain, several doctors in the private sector have also addressed common concerns. Among these doctors are Dr Adel Mohammad Yasin Al Sisi, Chief Medical Officer of Prime Health Care Group, Dr Atul Aundhekar, CEO of Avivo Health Care Group, Dr Abdul Karim Nasser, Specialist Pulmonoligst at Burjeel Speciality Hospital, Sharjah and Dr Mustafa Saif, Sepcialist Internal Medicine , Aster Hospital, Mankhool:

1. Is it advisable to mix and match doses from two different vaccines?

A: According to Dr Farida Al Hossani, official spokesperson of the UAE Health Sector and Director of Communicable Diseases, Abu Dhabi Public Health Centre, it is not advisable to mix and match doses of two different vaccines as there is not enough data or research available on this and there is no point to take such a risk.

Dubai Health Authority (DHA) has also tweeted against such a practice. In a tweet put out on their official Twitter handle @DHA on May 8, the health authority advised against taking a mixed dose of vaccines as there is no data to support such a practice.

2. What are different categories of COVID-19 vaccines available in the UAE?

A: We have two kinds of vaccines available in UAE- the inactivated virus-based vaccine where chemicals, heat or radiation are used to destroy the virus and this is introduced in the body to elicit an anti-body reaction. This technology is used to manufacture influenza and polio vaccines too.

The other - Messsenger Ribo Nucleic Acid (MRNA) vaccine is a new technology, where introduction of a part of the virus RNA is introduced in the human body to teach the immune system to make the ‘spike protein’ and protect against future infections.

3. Now that the health authorities have announced booster doses for people who may have taken the second dose in January, how do the booster doses work?

A: Booster doses increase immunity by re-exposing immunising antigen to the immune memory cells that have over a period of time lost their function or numbers.

What happens over a period of time post-vaccination is that the number of anti-bodies and their immunological reaction is reduced. Usually, the way the COVID-19 vaccine works is that it activates two parts of white blood cells namely, the first plasma B cells, which make antibodies lasting in the body for a few weeks and another type of cells - T cells that can identify and kill the pathogen. A booster dose can activate immunity for a longer time. Besides, some people will not respond as well as other people after two doses of the vaccine, so the booster dose will help as they do not only double the antibodies, but also have an exponential increment in antibody production, which can provide strong immunity against the virus.

4. Can a person who has taken two doses of an inactivated virus vaccine take an MRNA vaccine after a gap?

A: This is under study currently. Studies published in the Lancet Journal on ‘cocktail vaccines’ recently indicated that mixing and matching COVID-19 vaccine doses may increase reactogenicity. In clinical trials, this term refers to the property of a vaccine being able to produce common ‘expected’ adverse reactions, especially, excessive immunological responses and associated signs and symptoms such as fever and sore arm at injection site.

However, this is an ongoing trial with limited results. Given that many of the approved COVID-19 vaccines are highly effective, it is recommended that one follows regimes tested in clinical trials until more evidence is available.

5. If a person had COVID-19 after the second dose, does that mean he had no immunity and he has to repeat the entire process of two doses instead of taking a booster?

A: It indicates that the individual did not have strong antibody production to counter the impact of the virus or the exposure to the virus happened before the immunity had kicked in. Therefore, it is advisable that the individual repeats the entire first and second dose jab. Just a booster may not work in this case. However, the attending doctor decides on a case-by-case basis.

6. Can antibody test help minimise the need for a booster – should those with anti-bodies for COVID-19 go in for a third jab?

A: The health authorities are discouraging people from getting antibody tests done. Dr Hossani has said it is advisable for all to get their booster dose eight months after the completion of the second dose. It is free of charge like the first two doses and will provide a stronger immune reaction to the virus.

7. In the case of influenza, people are required to take the jab annually as every year the vaccine is set to accommodate mutants – will taking the booster of the same formulation actually protect against variants and mutants?

A: In case of the current booster dose, we definitely will have an exponential increase in antibody activity. However, the advent of a new variant will warrant a tweak next year, so an upgraded version of vaccine will be required. In case of a vaccine that introduces an inactivated virus in the human system, it introduces the exact sequence of amino acids of the virus in an inactivated form, in the body to induce an antibody reaction. So one cannot use the previous year’s inactivated virus, one will need fresh stocks of inactivated virus. The virus has evolved, so the vaccine evolves accordingly.

8. Will the COVID-19 vaccine be an annual feature like the seasonal flu vaccine?

A: So far, there is little data on this. However, going by the annual vaccination, we require against illnesses like influenza, which belongs to the coronavirus family, it appears tweaked vaccines would accommodate new variants and mutants to keep the immunity going strong.

9. Why are adolescents being administered the COVID-19 vaccine, if they are usually are not affected?

A: While COVID-19 has, so far, been seen to have a milder impact in teenagers and infants, the decision to vaccinate them was only taking recently. Thousands of school students in the age group of 12-16 have been able to get the COVID-19 vaccine under the vaccination campaign by the Ministry of Health and Prevention and most schools in the UAE plan to have all their students complete both doses of vaccination by June-end this year.

Global data points out that though most children with COVID-19 have mild or no symptoms, some children can get severely ill and may need hospitalisation. There are also rare severe cases of children dying from COVID-19 and its effects, including multisystem inflammatory syndrome. For vaccination to do its job, it is essential to vaccinate as many people who are eligible and getting adolescents vaccinated means their faster return to social activities. So why take a chance? It is best to vaccinate teenagers as well for a safer school environment. Although those affected might be asymptomatic, they can transmit the disease in the community.

10. Can youngsters in the age group of 12-16 years have any side effects such as allergic reactions or do vaccines affect their fertility?

A: It is a misnomer to say any vaccination can affect fertility, as the two are not connected. This is fear mongering as there is no clinical data to prove that any vaccine has had an impact on fertility, including the COVID-19 vaccine.

When it comes to allergy, age is no bar. Any age category, be it a toddler, an adolescent, a young adult or even an aged person could have a similar allergic reaction to a vaccine. This is not age-specific.

The most common side-effects are fever and feeling tired or achy. They are mostly short-lived up to 24 hours. Some allergic reactions can rarely develop if there is an allergy to any vaccine component.