RELATED: If You Got Moderna, This Is How Your Antibodies Respond to the Delta Variant. During a company earnings meeting on Aug. 5, Moderna said that breakthrough infections could possibly increase due to three factors: the Delta variant, mask and social distancing fatigue, and people moving indoors as summer ends. “We believe that increased force of infection resulting from Delta, non-pharmaceutical intervention (NPI) fatigue, and seasonal effects (moving indoors) will lead to an increase of breakthrough infections in vaccinated individuals,” the company said in published slides that accompanied the meeting. The Centers for Disease Control and Prevention (CDC) says breakthrough cases are expected with the coronavirus. Per a leaked July 29 document from the agency, there is currently a rate of about 35,000 symptomatic COVID infections per week among the more than 162 million fully vaccinated individuals in the U.S. More than three months ago, the CDC dropped social distancing and mask recommendations for vaccinated people, citing evidence that there was little risk of these individuals getting or spreading the virus. However, the agency changed its mask guidance last week, now recommending that vaccinated people continue to wear masks indoors when in areas of high or substantial transmission. This recommendation followed new CDC data showing that vaccinated people could potentially spread the same amount of virus as unvaccinated individuals. “Our vaccines are working exceptionally well,” Walensky told CNN’s Wolf Blitzer on Aug. 5. “They continue to work well for Delta, with regard to severe illness and death—they prevent it. But what they can’t do anymore is prevent transmission.” RELATED: For more up-to-date information, sign up for our daily newsletter. According to Moderna, its vaccine is 93 percent effective six months after the second dose. But the company does expect antibody levels to continue to wane over time, which will eventually impact effectiveness. Moderna now says they believe a third booster shot “will likely be necessary prior to the winter season,” especially given the continued spread of the Delta variant. But both the CDC and the World Health Organization (WHO) have recently advised against administering booster vaccines so soon. On Aug. 4, the WHO called for a moratorium on additional shots until the end of September at the earliest, in order to allow low-income countries the opportunity to vaccinate at least 10 percent of their populations. “The need for and timing of COVID-19 booster doses have not been established. No additional doses are recommended at this time,” the CDC states on its website. RELATED: If You’ve Done This, Your Risk of COVID After Vaccination Is 82 Times Higher.