July 26, 2021

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How long does each vaccine protect against Covit-19? This predictive model calculates it


Vaccines against COVID-19 were developed within a year. The challenge now is to know how long each vaccine provides protection and how strong it is. Duration can be an important factor in controlling infectious REUTERS / Dado Ruvic / Illustration

Australian researchers have provided a breakthrough in answering frequently asked questions surrounding the COVID-19 vaccine: how long safety in the real world lasts, not in controlled trials.

Issued by: Infopa

They are waiting for a peer review in a special journal – with predictive modeling techniques to assess the strength and duration of immune protection provided by seven different COVID vaccines. The results suggest that when a vaccine is administered as soon as it is administered, its protection lasts longer. However, they warn that vaccination strategies need to be adjusted to better address the problem of weakened immunity against the corona virus.

Scientists led by Miles Davenport of the Kirby Institute, which is part of the University of New South Wales in Sydney, Australia, have based their model on the hypothesis of raising high levels of neutral antibodies – a subgroup of antibodies that can be inactivated – associated with immune protection. This question came to the fore in previous research on the safety and efficacy of vaccine in rehabilitated Covit-19 patients.

They used data from vaccines produced by Pfizer-Bioentech companies from the United States and Germany, respectively; From Moderna, USA; Sputnik-V from Russia; Bharat Biotech, from India; Johnson & Johnson, from the United States; Astrogeneca; From England; And Coronavak, the synoform of China. They were able to define the level of levels of neutralizing antibodies produced by each vaccine within 250 days.

The researchers compared those pathways with recovered COVID-19 patients with natural immunity. In addition, they designed how low antibody levels might work against new strains of the corona virus. They used agile sera in particular to normalize vaccine data, which came from a variety of estimates in its original state, so it is difficult to combine them.

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The researchers hope that the modeling study will “help develop vaccine strategies to control the future course of the infection”. One issue to consider in vaccination programs is that protection against COVID-19 is not the same as protection against infection.

When the researchers examined the level of neutralization produced by each vaccine and fed the numbers into their sample, they found that protection against acute COV-19 was consistent, but protection against corona virus infection was significantly lower. They found that the reduced level of protection provided by the vaccine depends on the initial severity of the neutral antibody response.

The Australian study also raises concerns about the risk of higher cases of new strains of the corona virus, particularly in the UK, South Africa and Brazil. Those new strains are harder to neutralize than the original virus, which was discovered in Wuhan, China in January last year.

Numerous studies have already documented how the effectiveness of first-generation Covit-19 vaccines – in the days following immunization, even in its most potent form – is reduced against the South African variant in particular: they provide protection, but not to a previously proven extent by testing with the parent virus.

The forecast of Australian scientists took into account the problem of sample variations. It suggests that variants pose a greater threat to vaccines with a lower initial efficacy against the parent virus. Researchers predict that if the initial efficacy of a vaccine is 70%, for example, if the neutralization levels of the vaccine are reduced fivefold in the presence of a new variant, the efficacy will be reduced to only 25%.

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Another result that contributed to the work is that there will be differences depending on the level of neutral antibodies used in the vaccine. The Pfizer and Modern vaccines were very effective, with an initial efficacy of 95%, which did not decrease to 50% until 200 days. The Sputnik V vaccine maintained 70% efficacy at 150 days and 50% at 125 days.

Meanwhile, the Johnson & Johnson and AstraZeneca vaccines had 67 and 62% efficiencies, respectively, but reached 50% safety index on day 50. In contrast, the synoform coronavac vaccine is being administered in Chile. The vaccine had an initial efficacy of 50 percent, but according to the model they found safety after two or six months of administration.

However, the results do not mean that certain licensed vaccines should be rejected. They acknowledge that this study prediction is not recommended, but is based on imaginary algorithms derived from data available in the active sera.

Recent work in Covid-19 patients in Singapore has suggested that the duration of the neutral antibody response varies from individual to individual, with only a very small portion experiencing very long-lasting stability and no other antibodies.

Vector Romanovsky, a researcher at Gonzalez and vice-president of the Argentine Society of Virology, who consulted with Inbobe, commented that the study in Australia was “still peer review.” Therefore, it does not have the approval of long-term experimental sources that allow us to evaluate or correct the predictions / interpretations of the theoretical model ”.

Dr. Romanovsky noted, “It is valuable to face the study of models that allow predictions from simple data to obtain the level of protection that a vaccine candidate can provide. The fact is that there is still insufficient evidence for the relationship of protection between data based on the neutralization of antibodies as indicators of the immune response and the effectiveness of vaccines under study. ”

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According to a Gonzalez researcher, Australian scientists have “based their reports on the levels of neutralizing antibodies, which are one of the markers of the immune response and great interest”. He added: “I think they will forget about the cellular response and the memory of the immune system, which are important when dealing with an infection from a pathogen, against which the vaccine response was initially induced. Other studies by volunteers from clinical trials of vaccines do not seem to confirm these negative predictions with respect to some vaccines that have already been used. “

For his part, Humberto Depot, a virology researcher at the National Institute of Agricultural Technology (INDA), commented to Inbobe about the study in Australia: “The effort to explore two aspects of rigorous standardization and the possibility of prediction is interesting: contact protection neutralization assessments and disease in the Middle Ages Based on the modeling of resistance and antigenic drift and its correlation with the effectiveness of vaccines. Broadly speaking, the authors suggest that neutralization ratings are good predictors of vaccine protection. They also warn that a decrease in immunity in 250 days will allow for significant and infectious, but strong against severe disease.

Infographics: Marcelo Regalado