Omicron BA.2: mRNA based vaccines give protection that wanes with time, says UK-based study

The ‘stealth Omicron’, a sub-lineage of the Omicron BA.1variant is causing the worst Covid outbreak in China and South Korea since 2020 asking Indian health experts be on high alert over the impending fourth wave of the coronavirus pandemic in the country. However, to much respite, a new study says the mRNA vaccines can provide protection against Omicron BA.2  but its effects against symptomatic disease waves within months of a third dose.

India’s first mRNA-based Covid vaccine is being developed by Pune-based Gennova Biopharmaceuticals that recently submitted the phase -II and Phase -III trial data to the regulator Drugs Controller General of India (DGCI), sources said.

It has already been established by various studies that BA.2 spreads faster than BA.1 Omicron variant but it is still not clear if the stealth variant is more adept in evading the immunity provided by Covid-19 vaccines. But this yet to be peer-reviewed study, published on the preprint server medRxiv showed that people who received two doses of either the Pfizer–BioNTech or Moderna mRNA-based vaccine enjoyed several months of substantial protection against symptomatic disease caused by either BA.1 or BA.2.

The protection, however, waned to around 10 per cent after 4-6 months of the third dose of vaccination. This means that the vaccine after 4-6 months can only prevent infection in 10 per cent of the cases. The protection offered by the vaccines wane in a similar way for both the lineages of the variant and with another booster dose, protection of 30-60 per cent can again be achieved for both BA.1 and BA.2

Surveillance data collected in the United Kingdom too shows similar results of protection by vaccine limiting to less than 20 per cent for both subvariants after 15 weeks or more from the day of the second dose and after third dose, it rises roughly to 70 per cent 2-4 weeks post jab.

According to Laith Abu-Raddad, an infectious-diseases epidemiologist at Weill Cornell Medicine–Qatar in Doha and a co-author of the study, BA.2 was earlier thought to be more dangerous than BA.1 but the study results now give him hope that vaccines and booster doses can prevent worst Covid cases even for the new stealth variants.