Partial vaccination can be risky
While a single dose of either vaccine provides some benefits, relying on partial vaccination for people who are vulnerable or working in high-risk roles is problematic. It’s critical we fully vaccinate frontline health-care workers, quarantine workers and people who work and live in aged and disability care as soon as possible.
Another challenge is that all current COVID vaccines are based on the original virus strain but variants now make up the majority of infections in many countries. Some variants are targeted less effectively by vaccines, particularly after only one dose.
Preliminary data suggests that while two doses of the Pfizer vaccine are 88% protective against symptomatic infection with the B.1.617.2 variant, a single dose is only 33% effective.
A similar variant, called B.1.617.1, is behind the current outbreak in Victoria and may respond similarly. This makes it even more important to ensure frontline workers receive both vaccine doses as quickly as possible.
It’s also worth noting immune responses to one dose of either the Pfizer or AstraZeneca vaccines decrease with age.
In a pooled analysis of Pfizer and AstraZeneca, older people had lower rates of protection than younger people after a single dose, although older people were protected just as well as younger people after two doses.
Although this study is yet to be peer-reviewed, it tells us administering the second dose in a timely manner is particularly important for older people to realise the full benefits of vaccination.
Kylie Quinn, Vice-Chancellor's Research Fellow, School of Health and Biomedical Sciences, RMIT University and Jennifer Juno, Senior research fellow, The Peter Doherty Institute for Infection and Immunity
This article is republished from The Conversation under a Creative Commons license. Read the original article.