Africa-Press – Lesotho. Throughout the COVID-19 pandemic, which started when the first novel acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified during the outbreak in the China’s Wuhan in December 2019, people who fell victim to it, whether vaccinated or not, have often laid hopes that their antibodies might protect against a reinfection by new variants.
One of the questions people have asked since the start of the COVID-19 pandemic back in 2019 has been if one can rely on acquired immunity, besides vaccination, to safeguard them against new variants of the respiratory disease that continuously kept emerging.
Previous infection with so-called alpha, beta and delta variants did offer a quite high degree of protection, but this waned in the case of the omicron BA.1, a new study revealed.
Over the past few years, as COVID-19 marched relentlessly across the planet, it spawned alpha, beta, gamma, delta, omicron variants of the SARS‐CoV‐2 virus.
The fact is, ribonucleic acid (RNA) viruses like COVID-19 have small genomes, (estimated as about 10,000 bases) but a high mutation rate. As the virus infected a person, its genome, or genetic code, would undergo tweaks, or changes, called mutations.
As the whole scientific world struggled to contain the pandemic, medics mapped and shared the virus’ genetic sequences from patients. Some variants of the virus were able to claim an advantage that either allowed it to spread with greater ease, or enabled it to better dodge the host’s immune system.
That has been the case with omicron. The first dominant Omicron variant was BA. 1, boasting 35 mutations in its spike protein from the original SARS‐CoV‐2 variant dating to late 2019, when it was identified during the outbreak in China’s city of Wuhan.
Since it became the dominant variant globally, omicron (BA.1) veered off to create sub-variants worldwide. Hence, the pervasive speculations regarding immunity after one had already caught the respiratory disease.
What Is Natural Immunity? Y-shaped molecules – neutralizing antibodies – are generated after previous infection. They recognise intact proteins of the virus’s exterior and attach themselves to them. By doing so, they hamper the virus from gaining a foothold onto to the cell receptor – something that is necessary for infection.
But it isn’t just antibodies that can offer protection, as there are also T cells which can pick up where neutralizing antibodies failed, particularly in the case of omicron lineages boasting numerous mutations.
These are a type of immune cells able to home in on scraps of virus proteins rather than intact proteins. This means it would take many more mutations in the virus genome to completely evade the immunity of T cell, which wane more slowly than antibodies, and, as such, become tougher for omicron to dodge.
In the scientific review, findings of which were published in the the Lancet, scientists collected and scrutinized data from 65 studies carried out in 19 countries from the beginning of the pandemic until September 2022.
Primarily, the alpha, beta, delta and omicron BA.1 variants fell under the lens. The point of the study was to compare COVID-19 risk among individuals who had been infected previously and those who had not.
Research studying natural immunity in combination with vaccination was not part of the data analyzed. Furthermore, protection against reinfection, symptomatic disease, and severe disease (defined as hospitalization or death) were looked at separately.
Moderate protection from reinfection with omicron BA.1 (45 percent was offered by a previous infection, as compared with stronger protection against the pre-omicron variants of the virus (82 percent).
These findings were also true for symptomatic infection. Over a span of 40 weeks, protection against reinfection for pre-omicron variants dropped to 78.6 percent, added the study, while for omicron BA.1 it dropped more rapidly, plummeting to 36.1 percent.
In the case of severe disease, all variants displayed protection above 88 percent for 40 weeks. As for after the weeks period, there was limited data available for any conclusions to be made.
Interestingly, data showed that protection against severe disease after natural infection was comparable to that offered by two doses of COVID-19 vaccine for both pre-omicron and omicron BA.1 variants.
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