Variants of SARS-CoV-2

When a virus develops a new mutation, it is called a variant of the original virus. As viruses spread, they constantly change through mutations to their genetic code. Most mutations in the SARS-CoV-2 genome do not affect the functioning of the virus. However, mutations in the spike protein of SARS-CoV-2, which binds to receptors on cells lining the inside of the human nose, may make the virus easier to spread or affect how well vaccines protect people. Other mutations may lead to SARS-CoV-2 being less responsive to treatments for COVID-19.

Randomized Trial of a Third Dose of mRNA-1273 Vaccine in Transplant Recipients

In organ-transplant recipients, the standard two-dose vaccination strategy for coronavirus disease 2019 (Covid-19) has suboptimal immunogenicity.1 Both patients and health care providers have questioned whether a third-dose booster in transplant recipients would be safe and enhance immune response.2 We performed a double-blind, randomized, controlled trial of a third dose of mRNA-1273 vaccine (Moderna) as compared with placebo (the protocol is available with the full text of this letter at NEJM.org; ClinicalTrials.gov number, NCT04885907. opens in new tab).

Long-term Symptoms After SARS-CoV-2 Infection in Children and Adolescents

Children can experience SARS-CoV-2 postviral syndromes, but it is unclear to what extent these individuals are affected by long COVID. Evidence is predominantly limited to select populations without control groups,1-4 which does not allow estimating the overall prevalence and burden in a general pediatric population. We compared symptoms compatible with long COVID in children and adolescents (hereafter “children”) reported within 6 months after SARS-CoV-2 serologic testing.

Study Suggests Lasting Immunity After COVID-19, With a Big Boost From Vaccination

After an infection with SARS-CoV-2, most people—even those with mild infections—appear to have some protection against the virus for at least a year, a recent follow-up study of recovered patients published in Nature suggests. What’s more, this and other research demonstrates that vaccinating these individuals substantially enhances their immune response and confers strong resistance against variants of concern, including the B.1.617.2 (delta) variant.

Return to Play After COVID-19 Infection in Children

As the pandemic continues, children may experience long-term effects from COVID-19 infections. Because children may become “long haulers” or develop multisystem inflammatory syndrome in children (MIS-C), close monitoring after a COVID-19 diagnosis is important. In addition, children who are athletes require a separate return-to-play evaluation before they return to competitive sports or physical activities.