RELATED: 96 Percent of People Who Get the Pfizer Vaccine Have This in Common. The vaccines approved by WHO include Pfizer, Johnson & Johnson, AstraZeneca, Covishield, Moderna, Sinopharm, and Sinovac. Any vaccines outside of those seven will not be considered applicable by many colleges, putting students from two countries in particular in a difficult position. India has been administering the Covaxin vaccine and Russia has been giving the Sputnik V vaccine, neither of which have been approved by WHO, thus creating issues for the students who already received them. The New York Times reports that a Columbia University student residing in India who received the Covaxin vaccine was told that she needed to be revaccinated once she was in the U.S. However, the safety of receiving Covaxin with Pfizer, Moderna, or Johnson & Johnson—the three U.S.-approved vaccines—is unknown as there has been no research done on the combination of these shots. “Since COVID-19 vaccines are not interchangeable, the safety and effectiveness of receiving two different COVID-19 vaccines have not been studied,” Kristen Nordlund, a spokeswoman for the Centers for Disease Control and Prevention (CDC), told The New York Times in an email. She added that the CDC was recommending that those who received a vaccine that wasn’t approved by WHO should wait a minimum of 28 days before taking the first dose of one that is authorized by the organization. RELATED: For more up-to-date information, sign up for our daily newsletter. This issue is especially challenging for students in India, where COVID numbers have been surging and vaccine shortages are so significant that only three percent of the population is fully vaccinated, The Times reports. India sends the second-highest number of international students to the U.S., behind only China, with approximately 200,000 students. The only WHO-approved vaccine available in India is Covishield, but the gap between doses has been extended to 84 days, according to India Today, which could be too late for students’ U.S. arrival date. Additionally, the Covishield vaccine is in short supply in India. To assist students who attend U.S. universities, six regions in India have set up clinics allowing those heading to college stateside to get priority. Meanwhile, some colleges are allowing students who’ve received non-WHO-approved vaccinations to return to campus. For example, The New York Times reports that California State, the largest public university system in the country with nearly a half-million students, will accept any vaccination that was authorized by a regulatory agency. “They will be able to satisfy the requirement as long as the vaccine they receive is approved by something similar to an entity like the FDA,” Chancellor Joseph I. Castro told The New York Times. Axios reports Boston University and Johns Hopkins University will also welcome students who’ve received any vaccine approved worldwide.ae0fcc31ae342fd3a1346ebb1f342fcb RELATED: These 2 Vaccines Are Effective Against the New India Variant, Study Finds.