According to early data from the US Centers for Disease Control and Prevention (CDC), the latest Covid-19 vaccines, specifically formulated to target the Omicron variant XBB.1.5, have shown promising results in cutting the chances of getting a symptomatic infection by half. The vaccines have also been found to be effective against the JN.1 variant, which has been responsible for a majority of Covid-19 infections in the United States since late December.

To gather this information, researchers analyzed data from over 9,000 adults who were tested for Covid-19 at Walgreens and CVS Pharmacy locations between mid-September and mid-January. By testing for specific "quirks" in the virus, they were able to differentiate between different strains. The analysis revealed that the updated Covid-19 vaccines provided 54% protection against symptomatic infection among immunocompetent adults who were recently vaccinated, compared to those who did not receive an updated vaccine.

Ruth Link-Gelles, lead author of the study and head of the CDC's vaccine effectiveness program for Covid and RSV, expressed reassurance that the vaccines are providing the expected level of protection. While there is currently no estimate of vaccine effectiveness specifically for immunocompromised individuals, the fact that the vaccines are working in the general population brings reassurance for the whole population.

The main goal of the US Covid-19 vaccination program is to prevent severe disease. However, measuring vaccine effectiveness against symptomatic infection provides an early indicator of how well the vaccines are working. This early estimate is valuable as it allows for a larger population to be studied sooner, considering that more people get infected than are hospitalized.

Link-Gelles emphasized that the analysis confirmed the effectiveness of the vaccine against the JN.1 variant, which is currently the most common strain. The latest Covid-19 vaccines have been available since September, offering protection for about four months after vaccination. However, trends suggest that protection from the vaccine may wane over time. The CDC will continue to monitor vaccine effectiveness and conduct additional analysis to determine the duration of protection against severe disease.

Although wastewater data indicates that Covid-19 continues to circulate at high levels in the US, with tens of thousands of hospitalizations and hundreds of deaths each week, only about 1 in 5 adults and 1 in 9 children have received the latest Covid-19 vaccine. The CDC estimates that the vaccine is recommended for everyone aged 6 months and older. In comparison, nearly half of adults and children have received the flu vaccine this season. Link-Gelles emphasized that it is never too late to get a Covid-19 vaccine, as the added protection can go a long way in preventing hospitalizations and severe illness.

As the fight against Covid-19 continues, the latest data from the CDC highlights the effectiveness of the Covid-19 vaccines in reducing the chances of symptomatic infection. However, the importance of increasing vaccination rates to protect individuals and communities remains crucial in the ongoing battle against the virus.