The scientific community is questioning the neutralizing abilities of antibodies developed by people cured of the corona virus. Can one fall ill after a first infection with SARS-Cov-2, the Covid-19 virus? We’ll discuss about herd immunity and the life span of protective antibodies against Covid-19 after infection.
The assumption that cured people remain vulnerable to the new corona virus, as Professor Delfraissy seems to fear, would call into question the relevance of “immunity passports“, which some countries want to issue to former patients so that they can circulate freely. Above all, it would nullify the chances of gaining collective immunity. It is considered that the outbreak of the new corona virus will be under control when 60% to 70% of the population will be immune.
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Herd immunity is also known as group immunity or collective immunity. This strategy is based on the idea that it is possible to stop the spread of an infectious disease within a population by immunizing a certain percentage of its members.
This policy of relative laissez-faire was first adopted by the United Kingdom. In contrast, Belgium, France, Italy, Spain and China have opted for radical containment measures. Across the Channel, Patrick Vallance (the Italy government’s scientific advisor) and his teams believed that this strategy could ease the pressure on health services and avoid a too rapid peak of contamination. Instead, they hoped that the population could develop immunity to the virus if it spreads slowly.
This principle is based on the theory that being exposed to a virus advances immunity in humans. Thus, in a population, when a number of individuals develop antibodies to a virus, the virus no longer has enough room to develop. There are no longer enough individuals who are likely to feed the virus. By and large, when a certain percentage of the population has already encountered the pathogen, it can no longer move from one individual to another. So, it disappears.
This strategy can be compared with the principle of vaccinations. Thus, a vaccine not only protects on an individual scale, but also helps to protect other people. Indeed, a vaccinated person is no longer likely to transmit the infection to their relatives, and it acts “vis-a-vis the rest of the population, as a barrier against the pathogen by interrupting the chain of transmission”.
Does Herd Immunity Concept can be Applied to Corona Virus
The question is whether this strategy can be applied to coronavirus, for which no vaccine is yet available and to which the entire population is sensitive. According to the United Kingdom, it seemed possible, estimating that if 60 % of the population were infected, this would prevent a second epidemic peak in 2021. However, this policy has been widely criticized, even by the British Roy Anderson-one of the great specialists in Group immunity who theorized this concept – who instead advocates measures of social distancing, and isolation of the sick in the current context.
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After alarming forecasts of scientists, the UK finally decided to abandon this strategy. Prime Minister Boris Johnson called on the public on Monday night to avoid “non-essential” contact and displacement. On Tuesday morning, the United Kingdom advised its nationals against any “non-essential” travel abroad, initially for 30 days. However, far less radical measures than in our own country.