Why are there so many shortages of common vaccines?

This is an excerpt from Second Opinion, a weekly roundup of eclectic and under-the-radar health and medical science news emailed to subscribers every Saturday morning. If you haven't subscribed yet, you can do that byclicking here.

Canadians needing a jab in the arm might be scratching their heads about why they can't get certain vaccines these days.

Right now some people are reporting they've had trouble getting the new high-dose flu vaccine for seniors, the new shingles vaccine, hepatitis A and B shots, and even the rabies vaccine.

And for two years, travellers trying to get a yellow fever vaccine have faced delays in getting the shot, which is required to entersome countries in Africa and Asia.

So what's going on? Each vaccine has a different story. But the short answer is that either there has been a spike in demand somewhere in the world, or there has been a manufacturing problem that is interfering with supply.

"You don't necessarily know when there's going to be a shortage so you have to be quite agile to be able to overcome this," said Dr. Caroline Quach, pediatric infectious disease specialist and medical microbiologist at CHU Sainte-Justine in Montreal. "Because you don't usually know until it's often a bit late."

'It's been crazy'

The recent fluctuations in vaccine supply are making Daniela Mora's job even more hectic than usual. She is the national director for the Passport Health travel clinics, the largest chain of travel clinics in Canada.

"It's been crazy," she said,"2018 has been the year that vaccines were in shortage."

Canadians can get access to vaccines either through the public health system, including schools and doctors' offices, or through the private system, at pharmacies and travel clinics.

When manufacturers face shortages, they sometimes allocate the limited supply to the public system first.

So when Canadians discover they need specific vaccines for foreign travel, they might be surprised to learn that their local travel clinic can't give them everything they need.

"Yellow fever is actually one of the most concerning ones because we do have actual outbreaks going on," said Mora.

The mosquito-borne virus can cause a serious and sometimes fatal infection. Current yellow fever outbreaks in Brazil and some African countries have caused an increase in global demand.

Several countries require travellers to provide proof of yellow fever immunization before they can enter.

Health Canada warnsCanadians "to contact a designated Yellow Fever Vaccination Centre well in advance of their trip to ensure that the vaccine is available."

The yellow fever vaccine problems started back in 2016, because of a "disruption of the manufacture of the drug," according to the Drug Shortages Canada website. The estimated end date for the shortage is listed as "unknown."

That shortage, said Mora, is "really tough it's one of the only vaccines that's mandatory to get into certain countries."

Special flu vaccine for seniors

Canadians looking for the hepatitis A and B vaccines might also find they can't get them as easily as they thought. A combination of supply and demand problems have created shortages in many of the vaccines needed to prevent the viral liver infections when travelling abroad.

"With 30 clinics seeing hundreds of patients every week, it's been really tough. We have to allocate various doses almost on a daily or weekly basis. The demand is increasing," said Mora.

But it's not just travellers who are being told to wait. With the advent of flu season, there are questions in Ontario about the supply of a new high-dose vaccine recommended for seniors. Ontario is the only province to fund the vaccine specifically made forpeople 65 and older outside of hospitals and long-term care facilities.

Miriam Harris, a Toronto senior anxious to get the vaccine, went to her doctor two weeks ago but was told they'd run out.

"They said 'call in every day' and that's what I have been doing," she said.

But Harris still can't find out when the vaccine will be back in stock. "They don't know," she said.

After she notified the provincial health ministry, demanding to know when she could get the vaccine, she received a personal email from the province's immunization unit assuring her that there is no shortage. Doctors simply need to reorder. The high-dose flu vaccine is not available in Ontario pharmacies.

(The regular flu vaccine is available in pharmacies and there is no reported shortage.)

People have also been calling Passport Travel Clinics looking for the high-dose flu shot.

"I'm hearing from a lot of clients that their family doctors ran out of it," said Mora.

'Backorder' on new shingles vaccine

Seniors who want to receive the new shingles vaccine might also encounter shortages because so many people are asking for it this year.

After an intense marketing campaign which Second Opinion reported on last year, which saw bus and subway terminals covered with bright red ads for Shingrix, manufacturer GlaxoSmithKline (GSK) is trying to keep up with the demand.

"This high demand, coupled with variable timing for supply of additional doses, has created a temporary backorder status for the vaccine, which is expected to occur from time to time throughout the remainder of 2018 and into 2019," said GSK spokesperson Michelle Smolenaars Hunter in an email.

Shingrixwill be distributed "in a fair, equitable way," when more becomes available, she said.

Rabies?

A surprising name on the list of hard-to-find vaccines are those for rabies.

Right now the two companieslicensed to supply the rabies vaccine in Canada have reportedshortageson Drug Shortages Canada.

The rabies vaccine is recommended for travel to some countries in Asia and Africa, where there is a risk of exposure from domestic dogs.

Some health regions, including the Niagara Region, and the Northwestern Health Unit in Kenora, Ont., have issued notices about the rabies vaccine shortage.

GSK's RabAvertis in short supply because of an unexpected increase in demand that happened when supplies of an alternate vaccine by another manufacturer ran low. GSK predicts it will have more RabAvertby the end of the year.

Sanofi Pasteur Ltd.is also licensed to produce the ImoVax rabies vaccine in Canada. On Drug Shortages Canada the company lists the reason for the shortage as "disruption of the manufacture of the drug." That shortage is estimated to continue until next June with "supply disruptions anticipated in the private market. Product is under allocation."

'Chronic' problem

For doctors and public health officials, the rotating vaccine shortages are becoming a chronic situation.

"It's chronic in the sense that it happens from time to time but it's not always the same vaccine," said Quach. When it happens it's up to the federal and provincial health agencies to try to shift supply to where it's needed, or to come up with other substitution strategies.

"It's very difficult from a public health perspective and a physician perspective to foresee when it's going to come and what's going to come our way in terms of shortages."

And there are limits to how quickly vaccine supplies can be manufactured.

It's a complex process that can take between 10 and 26 months,according to Smolenaars Hunter.

"Every batch of GSK vaccines is subject to extensive review and only product that meets rigorous standards and regulations are released into the marketplace."

A spokesperson for Health Canada said in an email that the department "recognizes the importance of vaccines and the impact that supply disruptions can have on many Canadians and the healthcare system."