COVID-19 Updates: Moderna COVID-19 Booster Candidates, Novavax Vaccine Effective Against New Strain, and More

Doctor giving a senior woman a COVID-19 booster shot

At least 120 million cases of coronavirus (COVID-19) have been diagnosed worldwide as of Monday evening, March 15, 2021, including at least 2.66 million deaths. Healthcare officials in the United States have reported at least 29.5 million positive COVID-19 cases and at least 535,000 deaths. Source: Johns Hopkins University & Medicine

At least 359 million individual doses of COVID-19 vaccine have been administered worldwide as of Monday evening, including more than 107 million in the United States. Source: GitHub

Study evaluating Moderna COVID-19 booster candidates is underway

The first participants have been dosed with a modified COVID-19 vaccine that’s designed to address the potential need for booster vaccine candidates, in an amendment to the ongoing Phase 2 clinical study by Moderna Inc. The vaccine encodes for the prefusion stabilized spike protein of the variant B.1.351, first identified in the Republic of South Africa, and is being assessed as a booster vaccine to increase the breadth of response to emerging variants with key-receptor-binding domain (RBD) mutations. The multivalent vaccine candidate combines mRNA-1273, Moderna’s authorized vaccine against ancestral strains, and mRNA-1273.351 in a single vaccine, which is designed to elicit a broad immune response as both a primary series and when administered as a boost to those who have previously received mRNA-1273.

Previously published data has shown that vaccination with the vaccine produced neutralizing titers against all key variants tested, including B.1.1.7, first identified in the UK, and B.1.351, with a six-fold reduction in neutralizing titers against B.1.351, company officials said in a prepared statement.

Moderna officials have also announced that the first participants have also been dosed in a Phase 1 study of mRNA-1283, the company’s next-generation COVID-19 vaccine candidate. The candidate reportedly has potential to be a refrigerator-stable vaccine that could facilitate easier distribution and administration in more settings, including potentially for developing countries.

“We are pleased to begin this Phase 1 study of our next-generation COVID-19 vaccine candidate,” said Stéphane Bancel, chief executive officer. “Our investments in our mRNA platform have enabled us to develop this next-generation vaccine candidate. We remain committed to helping address this ongoing public health emergency.”

The mRNA-1283 encodes for the portions of the spike protein critical for neutralization, specifically the RBD and N-terminal domain, officials said. The study will reportedly evaluate three dose levels given to healthy adults as a two-dose series, 28 days apart, and a one-dose level given to healthy adults in a single dose. These will be compared with a two-dose series of mRNA-1273, the currently authorized dose level.

Novavax vaccine shows effectiveness against new strain

A COVID-19 vaccine by Novavax Inc. is reportedly one step closer to regulatory approval in the United Kingdom after seeing a 96% effective rate in preventing cases caused by the original version of the coronavirus in a late-stage trial conducted in the UK. According to a report by Reuters, there were no cases of severe illness or deaths among those who received the vaccine, and the vaccine was 86% effective in protecting against the more contagious virus variant first discovered and now prevalent in the UK, for a combined 90% effectiveness rate overall based on data from infections of both versions of the coronavirus.

The vaccine was also reportedly 55% effective in a smaller trial conducted in South Africa, where volunteers were primarily exposed to a newer, more contagious variant. The company expects to use the data to submit for regulatory authorization in various countries, although it is not yet clear when company officials will seek authorization in the United States or if regulators will require the company to complete an ongoing trial in the U.S. 

Vaccine “grace periods” and scheduling guidelines

Officials with the Centers for Disease Control & Prevention (CDC) state that vaccination providers should not use the “4-day grace period” guideline for the scheduling of the Pfizer-BioNTech and Moderna.

According to the CDC’s guidance, the recommended interval of the second dose of Moderna should occur 28 days after the first dose and the recommended interval of the second dose of Pfizer-BioNTech should occur 21 days after the first dose. The 4-day grace period should be used only when retrospectively evaluating records and not to schedule appointments. Appointments for a second dose should be scheduled to meet the recommended interval.

Interim clinical considerations for administration interval errors (defined as a second dose of Pfizer-BioNTech administered fewer than 17 days or fewer than 24 days for Moderna) call for providers to report the incidence to the Vaccine Adverse Event Reporting System. Patients are not to receive repeated doses in any of these incidences.

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