BA.2 is a new subvariant of the Omicron version of the coronavirus, and experts suggest that it is more transmissible,[1] harder to track, and causing a significant rise in corona virus disease (COVID)-19 cases in some countries such as the United States, which is estimated to be 23% of all cases. With rising cases of BA2.0 variant in the United States, centre of disease control has recommended the fourth dose for Pfizer and Moderna.[2] However, the latest study suggests waning immunity after the third dose of COVID vaccination.[3] A latest study in Israel suggested rates of confirmed COVID-19 and severe illness were lower following a fourth dose compared to only three doses.[4] However, a latest open-label, nonrandomized trial for the fourth dose using Pfizer and Moderna provided only a marginal increase in the protection as compared to the third dose.[5] The study also suggested a high viral load in infected individuals both in control and vaccine group arm, which suggests the fourth dose may provide a little benefit in transmission.
It has been predicted that BA2.0 will soon dominate the proportion of all COVID cases throughout the world. Recent reports suggest that BA.2 subvariant is more infectious and transmissible.[1,6,7] The effectiveness of the fourth dose against BA.2 is questionable as the studies revealed only a marginal increase in the protection from BA.1 using the fourth dose.
Experts suggest a rise in a number of BA.2 cases across the globe. However, health policy makers need to assess the situation carefully and take scientific decision on the use of the fourth dose against COVID-19.The decision is particularly important in the context of resource-poor and low- and middle-income countries.
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References
1. Available fromhttps://www.who.int/news/item/22-02-2022-statement- on-omicron-sublineage-ba.2[Last accessed on 04 Apr2022].
2. Available fromhttps://www.cnbc.com/2022/03/29/fda-authorizes-fourth-pfizer-covid-vaccine-dose-for-people-age-50-and-older-.html
3. Ferdinands JM, Rao S, Dixon BE, Mitchell PK, DeSilva MB, Irving SA, et al. Waning 2-dose and 3-dose effectiveness of mRNA vaccines against COVID-19–associated emergency department and urgent care encounters and hospitalizations among adults during periods of Delta and Omicron variant predominance—VISION Network, 10 states, August 2021–January 2022. Morb Mortal Wkly Rep 2022;71:255-63
4. Bar-On Y, Goldberg Y, Mandel M, Bodenheimer O, Amir O, Freedman L, et al. Protection by 4th dose of BNT162b2 against Omicron in Israel
5. Regev-Yochay G, Gonen T, Gilboa M, Mandelboim M, Indenbaum V, Amit S, et al. Efficacy of a fourth dose of covid-19 mRNA vaccine against omicron. N Engl J Med 2022;386:1377-80
6. Omicron BA.2 variant: Here’s what we know so far | World Economic Forum (weforum.org).Available fromhttps://www.weforum.org/agenda/2022/03/explainer-omicron-ba-2-variant/[Last accessed on 05 Apr 2022].
7. Atkulwar A, Rehman A, Imaan Y, Baig M. Analyses of Omicron genomes from India reveal BA. 2 as a more transmissible variant. medRxiv 20222022-04[Last accessed on 04 Apr 2022].
