A universal vaccine is needed to prevent future waves of COVID-19, study says

Newswise – Their findings underscore the need for more proactive planning and preparedness for future variants of concern (VOCs), including the development of a universal vaccine that can block SARS-CoV-2 infection and prevent serious illness.

As in many places, by February 2022 South Africa had experienced four distinct waves of pandemics caused by the original (or ancestral) SARS-CoV-2 virus and three VOCs – Beta, Delta and Omicron.

“These repeated pandemic waves have been fueled by new VOCs that undermine previous immunity either through infection or vaccination, increase transmissibility, or a combination of both,” said study author Wan Yang, assistant professor of epidemiology at Columbia University Mailman School of Public Health. New York, United States. “Although laboratory and field studies provide insight into various epidemiological features, quantifying the extent of immune erosion and changes in transmissibility for each VOC is challenging.”

To better understand the properties of the different COVID-19 VOCs, the team developed a mathematical model using weekly case and death data from nine South African provinces from March 2020 to the end of February 2022 to reconstruct the SARS-CoV-2 transmission dynamics .

They validated their model against three independent data sets and found that the estimated cumulative infection rates over time were roughly consistent with the serological data, and the estimated number of infections was consistent with the number of hospitalizations for all four pandemic waves caused by the ancestors , Beta, Delta and Omicron variants. The modeled infection figures were also consistent with the fatality rates of the ancestral, beta and delta waves, but less so for Omicron, since previous infections and vaccinations at this stage reduced the number of those infected with fatal outcomes.

Using data that emerged at the time of the new Delta and Omicron variants, the model was also able to predict the Delta and Omicron waves retrospectively before the real observed peak of cases and deaths from these VOCs. The team found that the model accurately predicted the remaining trajectories of cases and deaths in most of the nine provinces.

After validating their model, they then used it to estimate epidemiological characteristics for each VOC, including infection detection rates, infection mortality rates, population susceptibility and transmissibility, and compared these dynamics between provinces. These “model inferential estimates” were then used to quantify the immune erosion and increase in transmissibility for each VOC.

They found that the beta variant eroded immunity in about 65% of people previously infected with the ancestral SARS-CoV-2 and was 35% more easily transmissible than the original virus. This finding was supported by the experience of previously infected participants in one of the vaccine studies, who had a similar susceptibility to the beta variant as those who had no prior infection.

Estimates for Delta varied between provinces, but overall, the variant eroded immunity from previous infection or vaccination by about 25% and was 50% more transmissible. This is consistent with a reported 27.5% reinfection rate observed during the Delta Wave in Delhi, India.

Finally, estimates for Omicron have varied, but consistently highlighted its known higher portability than previous VOCs. The authors estimated that Omicron was about 95% more transmissible than the parent SARS-CoV-2 and compromised immunity (prior infections and vaccinations) by 55%.

These results illustrate that high prior immunity to SARS-CoV-2 does not preclude new COVID-19 outbreaks, as neither prior infection nor current vaccination completely blocks infection by a new variant.

Several worrying and interesting SARS-CoV-2 variants have emerged in the two years since the pandemic began, and it is difficult to predict the frequency and direction of future viral mutations, particularly the extent of immune erosion, changes in transmissibility and congenital disease severity, they say Yang and co-author Jeffrey Shaman, professor and director of the climate and health program at Columbia University’s Mailman School of Public Health. They add that VOCs other than alpha have previously caused some level of immune erosion, and later VOCs such as Delta and Omicron are more genetically distinct from earlier variants, making them more capable of causing re-infection despite various previous exposures and vaccination. Given this pattern, the authors suggest that there is an urgent need for a universal vaccine that can block SARS-CoV-2 infection and prevent serious illness.

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