Flu shot timing: What PCPs need to know
The estimated burden of the 2017-2018 influenza season was 48.8 million illnesses, 959,000 hospitalizations and 79,400 deaths, according to the CDC. To ensure that patients are protected throughout the influenza season, the timing of vaccination is critical.
“Because the flu season is very unpredictable in many ways, there’s a balance between the timing of vaccination and worries about how long protection may actually last,” Jeffrey S. Duchin, MD, health officer and chief of the communicable disease epidemiology and immunization section of public health for Seattle and King County, Washington, told Healio Primary Care.
Duchin and William Schaffner, MD, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center, spoke with Healio Primary Care about the importance of influenza vaccine timing and recommendations for the 2019-2020 influenza season.
Types of vaccines
Both trivalent and quadrivalent vaccines are available for the 2019-2020 influenza season, and the CDC does not express a preference for one over the other.
Schaffner noted that he is frequently asked which is better for adults aged 65 years and older — a quadrivalent vaccine or a high-dose trivalent vaccine.
Because previous studies have shown that the high-dose trivalent vaccine and the trivalent vaccine with adjuvant have provided superior protection throughout past influenza seasons, “we’re recommending one of those two vaccines for people aged 65 and older,” he said.
Duchin, who is also a professor in the division of infectious diseases at the University of Washington, agreed that high-dose or adjuvanted trivalent vaccines are preferred for those aged 65 years and older. For other adults, he explained that “here in Washington state, we advise that quadrivalent is preferable if available, but people should not forgo vaccination if trivalent is the only form available.”
Ideal vaccine timing
The CDC recommends that everyone aged 6 months and older should receive their influenza vaccine by the end of October to ensure protection throughout peak flu season.
Duchin noted that physicians should tell patients to get vaccinated by that time, but also that because “children 6 months through 8 years require two doses, they need to receive that first dose of that series as soon as it becomes available in their community so that they can be complete with the second dose by the end of October.”
He explained that because adults only receive one dose, telling patients to get vaccinated by the end of October is adequate.
Being vaccinated into mid-November would also ensure that patients receive adequate protection through March, Schaffner said.
However, Duchin explained that although being vaccinated later in the season still provides benefits to patients, the best way to avoid missing work, unnecessary doctor’s appointments, hospitalizations and even death is to receive the vaccine by the end of October.
Is it ever too late to be vaccinated?
With flu activity typically continuing into the spring, it is still beneficial for patients to receive the vaccine if they miss the recommended deadline.
“Last season we had a very large flu outbreak late in the season, so if you miss the October 31 deadline, it’s still very valuable to be vaccinated as long as flu activity is circulating in your community,” Duchin said.
Schaffner noted that after getting the vaccine, “it takes about 8 to 10 days for your protection to build up. So if we’re having a ‘typical’ influenza year and it peaks in February, you’ve still got time in December or even in January to get vaccinated.”
However, he explained that if patients find themselves unimmunized past the recommended deadline, they should “run, do not walk, and get yourself vaccinated.” – by Erin Michael
CDC. Estimated Influenza Illnesses, Medical visits, Hospitalizations, and Deaths in the United States — 2017–2018 influenza season. https://www.cdc.gov/flu/about/burden/2017-2018.htm. Accessed September 24, 2019.
CDC. Key facts about seasonal flu vaccine. https://www.cdc.gov/flu/prevent/keyfacts.htm. Accessed September 24, 2019.
CDC. Seasonal flu shot. https://www.cdc.gov/flu/prevent/flushot.htm. Accessed September 24, 2019.
Disclosures: Duchin reports no relevant financial disclosures. Schaffner reports being a member of the data safety monitoring board for Pfizer and consulting for Roche Diagnostics.