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Prof. Malavige on second jab, concerns over AstraZeneca and more
Prof. Neelika Malavige
The Sunday Times asked the Head of the Department of Immunology and Molecular Medicine, University of Sri Jayewardenepura, Prof. Neelika Malavige for her expert opinion on some questions our readers had.
Has the South African variant been detected in Sri Lanka?
Yes, the South African variant has been detected in Sri Lanka in a person who was in a quarantine centre on return from Tanzania. However, the ‘problematic’ mutation in this variant has also been found in the Sri Lankan lineage of the new coronavirus, in the Mahiyanganaya cluster.
Will such variants have an impact on the protection that people will get from the vaccine?
We have got the serum samples of these patients and we will be able to provide an answer to this vital concern within the next two weeks.
Can a person who has been vaccinated with one type of vaccine, get the second dose from a different type of vaccine?
The manufacturers say, “No, you cannot.” Both doses should be from the same type of vaccine. In the United Kingdom (UK), researchers are conducting a clinical trial on this – whether different vaccine doses can be used – and we should get the results in about two months.
Some countries though which have difficulties in securing large stocks of one type of vaccine are considering whether they can ‘mix and match’ different types of vaccines with regard to the two doses.
What happens if a person who gets the first dose, does not take the second dose?
There will be some immunity, but that will not be as good as when a person gets both doses. Usually, after the first dose, the immune response should begin to kick in about three weeks (about 21 days) later.
As soon as a person gets the vaccine, there is no instantaneous immune response. This is not only for COVID-19 vaccines but for all vaccines.
Studies have found that one dose of AstraZeneca vaccine gives a person 76% protection against symptomatic infection, while research in Scotland shows that one dose has had a ‘significant reduction’ in the number of people being hospitalized, having severe disease or dying.
Meanwhile, when an adequate number of people get immunized against a disease, there is a reduction in the transmission of that disease within that community. But there is a debate about what is ‘adequate’. Is it 70%, 80% or 100% of the people? It certainly won’t be 10% of the people as that will be inadequate to stop transmission.
No vaccine has laid claim that they can prevent asymptomatic infection, so even after a person gets the two doses of the vaccine, an RT-PCR test can become positive though the chances are “very, very less”, if fully vaccinated.
Even if a person who is fully vaccinated gets infected, the viral load is less. The quantity of virus in that person’s respiratory secretions is less, so transmission is less.
However, it is also important to follow the health guidelines – hand hygiene, face-mask wearing, social-distancing, cough and sneeze etiquette, etc. – strictly.
What if you have already got COVID, do you still take the vaccine?
The World Health Organization (WHO) guidelines as of now are that such a person should take the vaccine but may wait for about six months before doing so as it is rare for a re-infection with COVID-19 occurring in the first six months following an infection.
Data, meanwhile, are emerging that such a person may need only one dose to gain adequate immunity.
What happens if we don’t get the second dose, do we have to start all over again?
A person should try as much as possible to get the second dose at the stipulated time, but even if there is a ‘slight’ delay (about 2 months), that person need not start the full two-dose vaccination again. Such a slight delay in getting the booster does not create a major issue, but it would be good to take it on time.
Why has the rollout of the AstraZeneca vaccine in some European countries been halted?
Denmark has halted the vaccination since Thursday (March 11) after reports of one person dying of blood clots with several others facing the same issue after getting the vaccine.
Norway and Iceland followed Denmark as they too were using the same batch of vaccines, while Italy and Romania did so over safety concerns though they were using different batches.
When something like that happens, the vaccine rollout is halted for investigations to check whether such incidents are linked to the vaccine. The moment an ‘adverse event’ is reported, vaccination is halted, the issue looked into and the rollout resumed, if such an incident is not linked to the vaccine.
In Brazil, in October 2020, a participant in a clinical trial for AstraZeneca’s COVID-19 vaccine died, raising some concerns but it was found that he had not got the vaccine but a placebo (a substance which has no physical effects unlike the vaccine). Thus the trial was not suspended.
How is the virus transmitted?
The main modes of transmission are droplets and being air-borne. Some studies in Hong Kong have shown that 69% of infected people did not transmit the virus to even one other individual. However, 20% infected 80%, especially at super-spreader events such as weddings, funerals and large gatherings particularly in closed spaces with a lot of people.