Research shows that three or four doses of mRNA vaccine are still effective in preventing omicron infections

An international research team has provided one of the first realistic estimates of a vaccine’s effectiveness against omicron infections, regardless of symptoms or severity. From a serological survey of 5,310 blood donors and other volunteers, researchers estimated that three doses of the Comirnaty or CoronaVac vaccines were 48 percent or 30 percent effective, respectively, in preventing omicron infection immediately after vaccination, further improvement soon after the fourth dose.

Researchers expect protection from infection also associated with protection from transmission, and this is one of the first reports to show protection from transmission by a vaccine. omicron virus transmission. However, the effectiveness of the vaccine wanes rapidly after more than 100 days. Furthermore, the researchers estimated that more than 45% of the Hong Kong population was infected between January 1 and July 31, 2022. These findings were published in the journal Natural Medicine.

The omicron variant of SARS-CoV-2 demonstrated enhanced transmissibility and escaped vaccine-derived immunity. From January 1 to July 31, 2022, Hong Kong experienced an unprecedented fifth wave of COVID-19 infections, mainly due to the omicron BA.2 sub-variant. Since the likelihood of local transmission of COVID before 2022 is low, population immunity to SARS-CoV-2 in Hong Kong is almost entirely derived from the vaccine at the start of the wave.

There is ample data on how the COVID-19 vaccine strongly prevents serious illness, hospitalization, and death. However, several studies have investigated their effectiveness in preventing omicron infections, regardless of symptoms or severity. Infection prevention itself means preventing both asymptomatic and symptomatic transmission.

Combines results from a community-wide serological survey with 5,310 Blood donors and volunteers with SARS-CoV-2 viral load data from city-wide wastewater monitoring, the researchers estimated, (i) the vaccine’s effectiveness against all omicron BA.2 infections resulting from two, three and four doses of Comirnaty or CoronaVac homologous vaccines for 100 days after each dose and (ii) the attack rate of COVID-19 infection in Hong Kong from 1 May 1 to 31 July 2022. Researchers have developed two internal ELISA tests that detect IgG antibodies to the nucleocapsid (N) or Open Reading Frame 8 (ORF8) of SARS-CoV-2, with the test. The second test was developed specifically to detect previous infection in the CoronaVac vaccine.

The researchers estimated three and four doses of Comirnaty to be 48% and 69% effective, respectively, at preventing omicron infections, which, seven days after vaccination, fell to 26% and 35% at 100 days, respectively. after vaccination. Three and four doses of CoronaVac were 30% and 56% effective at seven days, respectively, falling to 6% and 11% after 100 days, respectively.

Meanwhile, the researchers determined that more than 45% local population in Hong Kong were infected with SARS-CoV-2 between January 1 and July 31, 2022 (i.e. an infection attack rate of 45%). Accordingly, the official case count, which combines both the Reverse Transcriptase-PCR test (RT-PCR) and the Rapid Antigen Test (RAT) results, has identified less than 41% of total infections.

The results indicate that booster vaccination using an mRNA or inactivated vaccine platform is effective in preventing short-term SARS-CoV-2 omicron BA.2 infection. This adds to previous studies that strongly demonstrate Vaccine effective in preventing serious illness and death.

Thus, mutation enhancement campaigns, especially with updated bivalent mRNA vaccines, can be strategically used to rapidly enhance population immunity when at risk. future episodes of infection arising from a related new virus variant. Relatively lower infection attack rate in Hong Kong in July 2022, compared with other overseas jurisdictions, highlighting the effect of continuing to add vaccination campaigns public health and social measures (eg, wearing a mask) to reduce disease transmission.