Are you due for your second dose of COVID-19 vaccine? Here’s what you need to know

Common questions answered as growing number of residents prepare for second dose

Dubai: As the UAE’s national vaccine campaign against COVID-19 progresses, over five milliion doses have been administered to UAE residents, free-of-charge in the last two-and-a-half months. Which means over 50 individuals per 100 people have received the vaccination. In the past 24 hours, as many as 103,469 residents have been vaccinated so far in the UAE, according to the Ministry of Health and Prevention. According to the World Health Organisation (WHO), the UAE is the second highest in the world in cumulative vaccine distribution rate.

The vaccination campaign, which kiched off in December 2020, will continue until December 2021, for a whole year. Giving this information while briefing the media, Dr Farida Al Khaja, chairperson of the COVID-19 steering committee at the Dubai Health Authority (DHA), said the vacciantion seeks to cover nearly 70 per cent of the population. The first phase of the campaign ends by March 2021 and the second phase will begin by April 2021.

Some UAE residents who received their first dose in December and January have already received their second dose. However, a large number of those who received their first dose in the second week of February are waiting for their second dose to take place in the stipulated 21 days. With many queries coming up in the process, Gulf News spoke to three specialists - Dr Anthony Thomas, pathologist and director, Prime Healthcare Group’s diagnostic division, Dr Atul Aundhekar, GP and CEO of Avivo Health Care Group and Dr Gunjan Mahajan, specialist clinical pathologist at Burjeel and Medeor Hospitals, to provide credible answers.

Q: Why do we have to wait for three weeks to get the second dose?

The COVID-19 vaccination has been designed as a two-shot process with the first dose providing a immunological memory to our immune system to recognise the invading virus. So by the time of the second dose, the immune response is in place and solidifies this act of fending off the virus. The three-week (21-day) gap between two doses has been stipulated in cases of most vaccines, as during the trials. The participants were administered the second dose in this period of time and the vaccine was found to be highy efficacious following this duration between the two doses. The vaccine makers, therefore, want to not only ensure the efficacy of the second dose but also make sure they are adding a second layer of protection to the body's immune system by adhering to the optimum 21-day gap. However, in cases of some vaccines, the Centre for Disease Control (CDC) is also allowing a 28- to 42-day gap.

Q. If a person tests positive after the first dose of the vaccination, what happens to the 21-day period for the next dose?

In this case, there are three categories:

a. Asymptomatic COVID-19 positive cases can get their second dose of vaccine after the specified quarantine period of 10 days.

b. Those with mild symptoms can be vaccinated with the second dose after 21 days from the day of positive PCR.

Dr Anthony Thomas

c. Those with severe symptoms or those required hospitalisation have to wait for three months for the second dose. Such people can go in for an antibody test and those having high antibodies can further delay the second dose. High antibody level indicates that the immune system has already generated the anti-bodies against the virus. Therefore, second dose can be deferred and taken under advice later.

Q. If two members of a family test positive and a third tests negative, should he or she go ahead with the second dose?

Dr Gunjan Mahajan

Yes, the individual should go ahead with vaccination after having completed the 10-day mandatory quarantine period. If a close contact does not test positive after this mandatory period, then he must go in for the second dose.

Q. If a person is feverish or suffering from very mild symptoms of cold, should he go for his vaccination?

It is not advisable for an individual to go for the vaccination under these circumstances. Instead, he should take a PCR test to rule out COVID-19. If negative, he should still wait to recover before going in for the vaccination. But he needs to inform the vaccination centre where he is scheduled for the second dose so that they can advise him about the optimum wait period.

Q. If a person tests positive after the second dose, what does that mean? Does it mean he will be required to do the vaccination all over again in two doses and when?

Immediately after the second dose, the immunity against COVID-19 may not be activated, so it is likely that an individual could catch the infection. Moreover, trials of all vaccines have indicated their efficacy is not a full 100 per cent. Therefore, it is possible to be infected even after second dose. This does not mean that the individual has to go in for another cycle. It is too early to give a definite opinion at this stage.

Q. How do we know if our vaccination is effective? Should we go in for the antibody test 15 days after the second dose?

Dr Atul Aundhekar

Antibody tests for the public have not been included in the general vaccine guidelines. In case of some MRNA vaccines in some cases, specific COVID-19 antigen test for the spike–protein may be carried out but very cautiously.

On the whole, antibody tests for the masses is not necessary as through the phases of the vaccine trials, their efficacy of 86-95 per cent is based on the biostatistics collected from such tests while the vaccine was in the trial phase. There is ample data that indicates that anti-bodies are generated. Insisting on anti-body test will not only amount to fear mongering by naysayers but also mean a very heavy and unnecessary cost on the health care system.

Q. If a person does go in for an antibody test and that test is positive after second dose, it is a sign that the immune system has worked against the virus and produced antibodies. However, if the anti-body test is negative, does it mean the vaccination was ineffective?

Presence of anti-bodies indicates the vaccination has been effective and has activated immunity. Meanwhile, a negative status can mean any of the following:

a. It may be too early an evaluation and may require waiting some for some more time.

b. Appropriate test was not conducted.

c. The individual’s immune response was poor.

We have to remember that this is the first time the human race has had to ponder upon so many factors in order to evaluate the efficacy of a vaccine. We will soon have definite answers for all these questions.

Q. What is herd immunity in simple terms?

Herd immunity refers to a kind of mass protection that a population acquires either through mass vaccination or by developing anti-bodies post infection.

The world has a population of approximately 7.8 billion, and going by the supply chain management for the vaccine doses, the World Health Organisation has estimated that by mid-2022 when most people across the globe would have been vaccinated, we can expect herd immunity against COVID-19 to be achieved to a good degree. What is true of the world is also true of each country.

Q. Can a person take one manufacturer for one dose and another for the second? If this happens by mistake, what is the side effect?

Viruses contain a core of genes containing the DNA or the RNA wrapped in a coat of proteins. The proteins coating the DNA or RNA are made by the messenger RNA, which is specific to that virus. The newly-approved mRNA vaccines (from Pfizer/BioNTech and Moderna) make this specific mRNA in the lab. Once injected in your arm, it "teaches" the body to trigger an immune response and creates the antigen when an infection occurs. Therefore, mRNA vaccines deliver instructions to our cells to make parts of viral proteins that does not harm the body, but only mimics a part of the coronavirus. This way, our immune system gets "trained" to recognise the protein and counters it with antibodies. When the real infection comes, these fighter cells are ready to take them down.

The other conventional vaccines, which use inactivated coronavirus (killed virus) actually help the body generate an immune response to the inactive strain by generating antibodies against this version.

The immune response to different varieties of vaccines is very different and getting two doses of two different vaccine can cancel out the impact. The manner in which the vaccines work is completely different and therefore mixing the two is not recommended. If a person accidentally happens to receive two different types of vaccine in two consecutive doses, it is likely that these may be ineffective. Such an individual must get an antibody test done to surmise if he or she has COVID-19 antibodies. If not, then the individual may have to go for a fresh round of vaccination after a gap under his doctor’s advice.