This is one of the first-ever studies to compare the protective strength of all coronavirus vaccines currently available in the USA.
The coronavirus (COVID-19) has mutated to produce a staggering 1,500 variants in the process of infecting over 270 million people worldwide. The latest variant, known as Omicron, is causing concern due to the speed of its spread and apparent resistance to current vaccines. Therefore, experts must test the efficacy of vaccines currently approved in the USA against this mutation.
A new study has achieved this. The white paper, which is still awaiting peer review, investigated which vaccine provides the most significant protection against the Omicron variant, if at all. The Moderna, Pfizer, and Johnson & Johnson (J&J) vaccines were tested by researchers from Massachusetts General Hospital – with findings suggesting that a complete vaccine series consisting of 2 injections followed by a booster shot several months later was the only protection available against Omicron.
The team stated that of the three vaccines tested, the Moderna and Pfizer mRNA vaccines offered the most protection against present and future variants, advising that recipients of the J&J vaccine will probably need more than one booster shot.
Previously, the researchers developed a test to understand differences in immunity produced by different vaccines against this constantly transforming disease. They used this assay to test the component of blood plasma left after clotting, known as sera – the best way to isolate and measure the number of disease-fighting cells known as antibodies in the blood.
All 239 participants had received either the mRNA-based Pfizer and Moderna vaccines or an adjuvant from J&J, which uses a deactivated part of the virus to produce an immune response. Of the individuals tested, seventy volunteers had received an mRNA vaccine booster six months after their primary vaccination series.
The scientists grouped participants according to whether they had a history of COVID infection and when they completed their primary vaccination series consisting of two injections (between 3 to 12 months earlier). Additionally, they ensured that boosted individuals had no history of COVID infection.
Remarkably, all three vaccine series resulted in undetectable neutralization of Omicron, but individuals boosted with either the Pfizer or Moderna mRNA vaccine could fight this strain.
The researchers also tested all three vaccines against the original virus known as COVID-19, which emerged in Wuhan in November 2019 – and the Delta variant, a virulent mutation first identified in India in late 2020.
Results showed that previously infected individuals who finished their vaccine series over six months ago exhibited higher levels of protection against COVID-19, Delta, and Omicron compared to those who had never had COVID – suggesting that previous infection proffers enhanced immunity. Despite this, boosted individuals with no history of COVID infection exhibit substantially higher immunity to Omicron than either of these groups.
The researchers found that the Moderna and Pfizer mRNA vaccines offer significantly greater immune responses against all variants than the J&J vaccine. To counter this, the group says that a booster shot can improve protection rates of recipients of the J&J series but add that this won’t match the level of antibodies seen with mRNA primary vaccination followed by mRNA booster. Taken together, this suggests that recipients of the J&J vaccine series may need additional mRNA boosters to raise antibody levels in the blood.
The extensive study established that Omicron is more infectious than any other variant tested. With assay results indicating that this variant is nearly four times more infectious than COVID-19 and twice as infectious than Delta. However, the results suggest that the Omicron infection is less severe than COVID-19 or Delta, but it should be noted that the results involve fully vaccinated individuals.
In the long term, volunteers fully vaccinated with Moderna over six months ago had higher levels of antibodies in their sera than those opting for Pfizer. But this made no difference when dealing with Delta, which saw all recipients of vaccine series over six months ago lose the ability to neutralize this variant – with only those fully vaccinated under three months ago or recently boosted able to fight it.
Overall, the group concludes that receiving the booster dose of an mRNA-based vaccine appears to be the only defense against Omicron and the Delta variant for long-term protection. Furthermore, they feel that widespread booster programs could curtail any variant set to emerge in the future.
Source: medRxivMedical photo created by freepik – www.freepik.com
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