[1] World Health Organization. COVID-19 weekly epidemiological update edition 90, published 4 May 2022. https://apps.who.int/iris/bitstream/handle/10665/353976/nCoV-weekly-sitrep4May22-eng.pdf?sequence=1&isAllowed=y. [2022-5-5].https://apps.who.int/iris/bitstream/handle/10665/353976/nCoV-weekly-sitrep4May22-eng.pdf?sequence=1&isAllowed=y
[2] Tegally H, Moir M, Everatt J, Giovanetti M, Scheepers C, Wilkinson E, et al. Continued Emergence and Evolution of Omicron in South Africa: New BA.4 and BA.5 lineages. medRxiv 2022. http://dx.doi.org/10.1101/2022.05.01.22274406CrossRef
[3] Khan K, Karim F, Ganga Y, Bernstein M, Jule Z, Reedoy K, et al. Omicron sub-lineages BA.4/BA.5 escape BA.1 infection elicited neutralizing immunity. medRxiv 2022. http://dx.doi.org/10.1101/2022.04.29.22274477CrossRef
[4] Cao Y, Yisimayi A, Jian F, Song W, Xiao T, Wang L, et al. BA2.12.1, BA.4 and BA.5 escape antibodies elicited by Omicron infection. bioRxiv 2022. http://dx.doi.org/10.1101/2022.04.30.489997CrossRef
[5] Outbreak.info. Lineage | Mutation Tracker: BA.4 Lineage Report. https://outbreak.info/situation-reports?pango=BA.4. [2022-5-8].https://outbreak.info/situation-reports?pango=BA.4
[6] GASAID. hCoV-19 tracking of variants (menu option BA.4). https://www.gisaid.org/hcov19-variants/. [2022-5-8].https://www.gisaid.org/hcov19-variants/