COVID-19 isolation testing (FOI)

Request

This came out today:

Deputy Medical Officer for Health, Dr Ivan Muscat, said: "Allowing Islanders to test themselves earlier in their isolation benefits both the health and wellbeing of individuals and the community as a whole.

"Current evidence shows that viral infection reduces quicker in those who are fully vaccinated, and the risk of spreading the virus to others is highest at the start of infection or just after the onset of infection. Therefore, it is appropriate that fully vaccinated Islanders are able to start testing themselves from day five whereas those who are not fully vaccinated may start testing themselves from day seven."

Please could I have the evidence that shows the viral infection reduces quicker.

Response

It is accepted that vaccinated individuals who become infected with COVID-19 can shed infectious viral particles. However, viral loads decrease faster in vaccinated individuals as compared to unvaccinated individuals^{[1] [2]}. Additionally, a further study^[3] has also shown that breakthrough infections clear more rapidly in vaccinated individuals, in around five and a half days compared with seven and a half days in unvaccinated individuals. Thus there is a lower and shorter risk of transmission from vaccinated individuals^[4]. Similarly, a study^[5] investigating household transmission in Denmark found increased transmission (secondary attack rates) in households of unvaccinated individuals and reduced transmission in households of individuals who had received a booster dose of vaccine compared to households of individuals who completed the primary vaccination series without getting a booster.

^[1] Chia, P.Y., Ong, S.W.X., Chiew, C.J., Ang, L.W., Chavatte, J.M., Mak, T.M., Cui, L., Kalimuddin, S., Chia, W.N., Tan, C.W. and Chai, L.Y.A., 2021. Virological and serological kinetics of SARS-CoV-2 Delta variant vaccine-breakthrough infections: a multi-center cohort study. Clinical Microbiology and Infection.

^[2] Singanayagam, A., Hakki, S., Dunning, J., Madon, K.J., Crone, M.A., Koycheva, A., Derqui-Fernandez, N., Barnett, J.L., Whitfield, M.G., Varro, R. and Charlett, A., 2021. Community transmission and viral load kinetics of the SARS-CoV-2 delta (B. 1.617. 2) variant in vaccinated and unvaccinated individuals in the UK: a prospective, longitudinal, cohort study. The lancet infectious diseases.

^[3] Kissler, S.M., Fauver, J.R., Mack, C., Tai, C.G., Breban, M.I., Watkins, A.E., Samant, R.M., Anderson, D.J., Metti, J., Khullar, G. and Baits, R., 2021. Viral dynamics of SARS-CoV-2 variants in vaccinated and unvaccinated persons. New England Journal of Medicine, 385(26), pp.2489-2491.

^[4] Bergwerk, M., Gonen, T., Lustig, Y., Amit, S., Lipsitch, M., Cohen, C., Mandelboim, M., Levin, E.G., Rubin, C., Indenbaum, V. and Tal, I., 2021. Covid-19 breakthrough infections in vaccinated health care workers. New England Journal of Medicine, 385(16), pp.1474-1484.

^[5] Lyngse, F.P., Mortensen, L.H., Denwood, M.J., Christiansen, L.E., Møller, C.H., Skov, R.L., Spiess, K., Fomsgaard, A., Lassauniere, R., Rasmussen, M. and Stegger, M., 2021. SARS-CoV-2 Omicron VOC Transmission in Danish Households. medRxiv.