COVID-19: the variants, the contagious phases and the vaccination

SARS-CoV-2, the virus that causes COVID-19, has had a major impact on human health globally. As of April of 2021, it has infected hundreds of millions, caused severe cases of disease and, in somes instances, inflicted long-term health sequelae, resulting in death and excess mortality, especially among older and vulnerable populations. Professor Philippe Colson, Associate Professor of Pharmaceutical Sciences and Microbiology and researcher in the IHU Méditerranée Infection, answered some of the most frequent questions.

What is a variant? With all these variants, can we talk about different epidemics?

Variants are viral strains in which major or minor mutations happened. The SARS-CoV-2 virus can take several different forms and, as of today, more than 15 variants of the initial strains have been described. What we observe is that immunity against one variant is not necessarily transposable to all the others.

The perfect example for this is Manaus city, in Brazil. In 2020, more than 75% of the population had been immunized against one form of the SARS-CoV-2, but, by the beginning of 2021, a new “Brazilian” variant appeared. The number of cases increased considerably again as if that 75% immunization had never existed.

Therefore, we could say that each new variant is responsible for an epidemic and that there is not one, but multiple COVID-19 epidemics worldwide.

How long after we have been infected with the virus do we become contagious?

The period between infection and symptoms, also known as the incubation period, is thought to be 2 to 14 days. However, people usually experience symptoms 4 to 5 days after exposure to the virus. It is thought that people may be contagious up to 48 hours before experiencing any symptoms.

Are asymptomatic patients less contagious?

There is still ongoing research on this key question and researchers still have not reached a consensus. Approximately 20% of the infected people will be asymptomatic, but what is their role in viral spreading? Well, there are 2 hypotheses (mechanical and biological) to consider:

  • Patients without symptoms will be less likely to spread their secretions through sneezing, coughing and, therefore, mechanically there is less chance of transmitting the virus;
  • Also, experiencing no symptoms could be a result of having a smaller viral load (as shown in Cevik et al. meta-analysis) and, thus, being less likely to infect other people.

Although they are less likely to transmit the virus, since they feel physically good, if they keep on going out and meeting with people instead of self-isolating, their “transmission-rate” will be as high as other symptomatic patients. Thus, the take-home message is that these people should not think that they are free of social distancing and wearing masks, just because they do not experience any symptoms.

Will children be able to get vaccinated? And pregnant women? Is that in our best interest in order to fight the pandemic?

Pfizer/BioNTech launched a trial for children for their mRNA vaccine Comirnaty. However, Los Angeles, in the USA, enabled vaccination for anyone over 16 years old.

I think that pregnant women represent a minor proportion of our population and them not being vaccinated will not affect the goals of the vaccination strategy, which is to protect the elderly and those at risk of being severely affected by the virus. Plus, women over 6 months pregnant usually rest at home, making them weak transmitters of the disease. Also, there is a consensus among researchers regarding the benefit-risk ratio, which is not favorable in the vaccination of pregnant women.

How long will the vaccines last?

This is impossible to know from clinical trials and other studies. Our best ally in answering this question is real-life data.

One of the first countries where vaccination started was Israel, so maybe what happens there will be a great source of information regarding how long the vaccines will last.

Can I relax on social restrictions if I am vaccinated?

No, certainly not or at least not for now. The vaccines have a high efficiency rate, but it is not 100%. Also, we must not forget that being vaccinated does not mean others are too, since vaccinating a whole country can be a lengthy process. Vaccines will certainly help reducing daily infections and death induced by COVID-19, but it must not be seen as a sufficient measure.

Philippe Colson

Associate Professor of Pharmaceutical Sciences and Microbiology

Researcher in the IHU Méditerranée Infection