December 4 2021
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Delta Variant

Covid-19 vaccines hold strong against Delta, protection waning in older adults

Story by Asiaone

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Published on September 13, 2021 10:01 AM
CHICAGO - Three US studies suggest Covid-19 vaccines offer strong protection against hospitalisation and death, even in the face of the highly transmissible Delta variant, but vaccine protection appears to be waning among older populations, especially among those 75 and older.

US data on hospitalisation from nine states during the period when the Delta variant was dominant also suggests that the Moderna Inc vaccine was more effective at preventing hospitalizations among individuals of all ages than vaccines from BioNTech/Pfizer Inc or Johnson & Johnson.

In that study of more than 32,000 visits to urgent care centers, emergency rooms and hospitals, Moderna's vaccine was ...


Moderna COVID-19 vaccine

The Moderna COVID-19 vaccine , codenamed mRNA-1273 and sold under the brand name Spikevax, is a COVID-19 vaccine developed by Moderna, the United States National Institute of Allergy and Infectious Diseases and the Biomedical Advanced Research and Development Authority . It is authorized for use in people aged twelve years and older in some jurisdictions and for people eighteen years and older in other jurisdictions to provide protection against COVID-19 which is caused by infection by the SARS-CoV-2 virus. It is designed to be administered as two or three 0.5 mL doses given by intramuscular injection at an interval of at least 28 days apart. It is an RNA vaccine composed of nucleoside-modified mRNA encoding a spike protein of SARS-CoV-2, which is encapsulated in lipid nanoparticles.

It is authorized for use at some level in many countries.

On 15 March 2021, Moderna's second COVID-19 vaccine started phase I clinical trials. This vaccine candidate can potentially be kept in refrigerators instead of freezers, making distributions easier especially in developing countries.

Medical uses

The Moderna COVID-19 vaccine is used to provide protection against infection by the SARS-CoV-2 virus in order to prevent COVID-19.

The vaccine is given by intramuscular injection into the deltoid muscle. The initial course consists of two doses. The World Health Organization recommends an interval of 28 days between doses. Data show that first dose efficacy persists for up to ten weeks. Therefore, to avoid deaths where supplies are limited, the WHO recommends delaying the second dose by up to 12 weeks to achieve high coverage of the first dose in high-priority groups. A third dose can be added after 28 days for immunocompromised people in some countries


A vaccine is generally considered effective if the estimate is =50% with a >30% lower limit of the 95% confidence interval. Preliminary data from a study in Minnesota suggest that the vaccine remains effective against hospitalization and asymptomatic infection by the Delta variant. From January to July 2021, the dominant variant in Minnesota shifted from Alpha in January, with a prevalence of 85%, to Delta in July, with a prevalence of 70%. Effectiveness against hospitalization by any variant fell slightly, from 92% over the entire period to 81% in July. Effectiveness against asymptomatic infection by any variant also fell only slightly, from 86% over the entire period to 76% in July. By comparison, effectiveness against asymptomatic infection by any variant fell further for the Pfizer–BioNTech vaccine, from 76% over the entire period to 42% in July.

On 27 August, the Centers for Disease Control and Prevention published a study reporting that the effectiveness against infection decreased from 91% to 66% when the Delta variant became predominant in the US, which may be due to unmeasured and residual confounding related to a decline in vaccine effectiveness over time.

Specific populations

Limited data are available on the safety of the Moderna COVID-19 vaccine for people who are pregnant. The initial study excluded pregnant women or discontinued them from vaccination upon a positive pregnancy test. Studies in animals found no safety concerns and clinical trials are underway to evaluate the safety and efficacy of COVID-19 vaccines in pregnant people. Real-world observations through the CDC v-safe tracking program have not uncovered unusual numbers of adverse events or outcomes of interest. Based on the results of a preliminary study, the US CDC recommends that pregnant people get vaccinated with the COVID-19 vaccine.

Adverse effects

The World Health Organization stated that 'the safety data supported a favorable safety profile' and that the vaccine's AE profile 'did not suggest any specific safety concerns'. The most common adverse events were pain at the injection site, fatigue, headache, myalgia , and arthralgia .

The US Centers for Disease Control and Prevention has reported anaphylaxis in 2.5 cases per million doses administered and has recommended a 15-minute observation period after injection. Delayed cutaneous reactions at injection sites resulting in rash-like erythemas have also been observed in rare cases but are not considered serious or contraindications to subsequent vaccination. The incidence rate for local adverse erythema is about 10.8%, in 1.9% of cases redness may extend to a size of 100mm or greater.

On 23 June 2021, the US CDC confirmed that myocarditis or pericarditis occurs in about 13 of every 1 million young people, mostly male and over the age of 16, who received the Moderna or the Pfizer–BioNTech vaccine. Most affected individuals recover quickly with adequate treatment and rest.

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