Updated: February 14, 2021 8:23:17 am
On Friday, France’s health authority, the Haute Autorité de Santé (HAS), said those people who have already been infected with COVID-19 should receive only one dose of the vaccine.
Right now, the vaccines that are in use globally, which include Moderna, Oxford/AstraZeneca and Pfizer-BioNTech, are all administered in two doses a few weeks apart. A second booster dose is required to build stronger and longer immune memory.
The US Centers for Disease Control and Prevention (CDC) recommends vaccination for people who have already recovered from COVID-19 because natural immunity may not last for a long period.
So, what has France advised?
The advisory says that people who have developed natural immunity after having recovered from a previous COVID-19 infection, be it symptomatic or asymptomatic, which has been proved by an RT-PCR or antigen test, should be considered immune from a repeat infection for a period of at least three months.
For such people, the advisory says that the vaccination should be carried out after this initial period of three months but preferably within six months of having recovered.
Further, such people will only be administered one dose of the vaccine. The reasoning behind this move is that people who have already recovered from the disease have already developed an immune response. Therefore, based on the current knowledge about post-infection immunity from COVID-19, such people need only a booster shot.
In case of prolonged COVID symptoms, however, if a person should be vaccinated will be decided on a case-by-case basis. This is called long-COVID and it means that the person may experience some COVID-19 symptoms months after first acquiring the infection. It is not known yet if vaccines have any impact on people suffering from long-COVID.
COVID-19 and vaccine rollout in France
About 2.2 million people in France have received one dose of the vaccine so far in what is being seen as a slow rollout considering the country has a population of 67 million. The country has recorded about 3.4 million cases of the virus and over 80,000 deaths. As per the health authority’s most recent update, the virus is circulating at a very high level in the country, “implying a persistent tension in the hospital system”.
Which coronavirus vaccines are France using?
The European Medicines Agency (EMA) has approved Pfizer-BioNTech, Oxford/AstraZeneca and Moderna vaccines.
Recently, the HAS recommended Moderna and Pfizer-BioNTech vaccines for people aged 65 and above, and to use the AZD1222, which is an mRNA vaccine and is produced jointly by the Swedish-British company AstraZeneca and the University of Oxford, for people below the age of 65 since there is lack of data on how this vaccine impacts older people.
This vaccine was granted a conditional marketing aurhorisation under a centralised procedure in the European Union on January 29, of which France is a member country. The vaccine has an efficacy of 62.17 per cent in reducing symptomatic infection after a standard two-dose regimen.
The Moderna and Pfizer vaccines are also mRNA (messenger RNA) vaccines. These vaccines, once injected into the body, instruct human cells to create copies of the spike protein, a number of which protrude from the surface of the SARS-CoV-2 virus. It is this spike protein that makes it easier for the virus to attach itself to receptors in human cells after which it starts infecting the person.
But this is exactly what an mRNA vaccine will stop the spike protein from doing. After the vaccine has instructed the cells to make copies of the spike protein, the body’s immune response is triggered, which in turn kicks off the building of neutralising antibodies.
Now, in case the virus enters the body of a person vaccinated with an mRNA vaccine, the body will already have antibodies, which should stop the spike protein from infecting the body’s cells.
What do we know about the effectiveness of a single vaccine dose?
According to an analysis published in the British Medical Journal (BMJ), early reports from Israel, which has vaccinated more than 75 per cent of its older people with at least one dose of the Pfizer BioNTech vaccine, suggest that the first dose led to a reduction of over 33 per cent in cases of coronavirus.
A recent literature analysis by Nature concluded that a single shot of either the Moderna or the Pfizer vaccine provokes a strong immune response against an emerging variant of the virus, as per tests in people who have recovered from COVID-19. After a single dose of either of the vaccines was administered in these people, the levels of neutralising antibodies against both the original SARS-CoV-2 virus and the emerging variant were found to be 1000-fold more.
The idea to administer single doses stems from the logistical challenges associated with COVID-19 vaccines, especially since vaccine supplies are limited. A Lancet paper on health policy highlights that it is not enough for countries to license vaccine usage, but there are greater challenges which include producing vaccines at scale, pricing them reasonably and allocating them where they are needed globally.
In the paper, the authors call for a more equitable approach to vaccine allocation, which is one of the ways in which the pandemic can be ended since the idea is to have fewer hosts for the virus to be able to infect worldwide.
They also note that single-dose vaccines that can be stored at refrigerated temperatures, such as one which is being developed by Johnson and Johnson should make deployment easier in resource-constrained settings.
What we don’t know about COVID-19 vaccines?
One of the biggest unknowns about vaccines is how long immunity will last after they have been administered. Therefore, it is not clear if people will need to be vaccinated every year or every few years.
It is also not clear if vaccines will reduce transmission of the disease since even vaccinated people are presumed to carry the virus in their nose and throat and shed it, thereby potentially infecting other people.
Therefore even vaccinated people still need to follow social distancing and wear masks. Further, because of how the virus is evolving into new variants that are believed to be more infectious (for instance the strain of the virus first identified in the UK is thought to be 25-40 percent more infectious), there is uncertainty regarding how effective the current vaccines will be against the new strains.
But for now, given that vaccine supplies are limited, the WHO has recommended that first priority should be given to those 65 years or older and those facing a high risk of exposure. This week, it recommended the Oxford/AstraZeneca vaccine for all adults. As of now, it is not known if this particular vaccine has any substantive effect on viral shedding or transmission.
Significantly, even as millions of doses of various vaccines have been administered worldwide, it will take a few years to vaccinate the entire world population, therefore, the virus will likely become endemic, which means it will keep circulating and people who do not have natural immunity and neither have been vaccinated will continue to remain vulnerable till then.
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