Third COVID vaccine dose increases protection, CDC studies confirm
While the SARS-CoV-2 Omicron variant has rapidly spread to almost every corner of the globe and is yet another cause for alarm worldwide, a third COVID-19 (COVID) vaccine dose has been shown to significantly restore protection from infection and hospitalisation against Omicron, according to three new studies from the US Centers for Disease Control and Prevention (CDC).
The first new CDC study compared two-dose and three-dose vaccine effectiveness between the Delta and Omicron variants. Data on COVID-related hospitalisations and emergency room visits from August 2021 to early January 2022 illustrate how two doses of an mRNA vaccine are significantly less protective against severe disease from Omicron compared to Delta. However, a third dose notably increases that protection against both variants.
The data found two doses of the vaccine were 76% effective at preventing emergency room and urgent care visits for Delta infections after six months – that protection dropped to 38% in the face of Omicron, but a third mRNA vaccine dose lifted protection back up to 82%.
The first study also found two-dose protection from hospitalisation was similarly low against Omicron compared to Delta (81% vs 57%). A third dose spiked effectiveness up to over 90% against both variants.
The second CDC study focused COVID infections and deaths from April 2021 to December 2021. At the peak of the Delta wave the study found two-dose vaccination reduced risk of death from COVID 12-fold and three-dose vaccination reduced risk of death 53-fold, compared to the unvaccinated.
Again, a third vaccine dose was found to significantly reduce a person’s chances of Omicron infection compared to two-dose vaccine; and while protection from Omicron death was still strong after two-doses, a third vaccine dose spiked protection from COVID death up to 98%.
The third and final study, recorded in the month from early December 2021 to early January 2022, revealed those receiving three vaccine doses were 66% less likely to develop a symptomatic Omicron infection compared to those receiving two vaccine doses. The severity of disease in the two-dose cohort was significantly decreased compared to the unvaccinated.
The study homed in on 70,000 symptomatic COVID cases in the US and pointed out those more than six months past their second vaccine dose were as likely to develop a symptomatic Omicron infection as those unvaccinated, although much less infectious compared to a breakthrough infection after two doses.
As a takeaway, the CDC recommends all Americans over the age of 12 to receive a third COVID-19 vaccine dose five months after their second dose. Less than half of Americans eligible for a third vaccine dose have taken up the free shot.
“These reports add more evidence to the importance of being up to date with COVID vaccinations – that means getting primary series and boosted when eligible to protect against severe COVID-19,” said CDC Director Rochelle Walensky.
Read: Japanese government to give COVID-19 vaccine boosters six months after second dose
